diff --git a/accessible/src/base/nsAccessible.cpp b/accessible/src/base/nsAccessible.cpp
index 77a7033e42f3..1382566df144 100644
--- a/accessible/src/base/nsAccessible.cpp
+++ b/accessible/src/base/nsAccessible.cpp
@@ -686,16 +686,16 @@ nsAccessible::GetStateInternal(PRUint32 *aState, PRUint32 *aExtraState)
   if (aExtraState)
     *aExtraState = 0;
 
-  PRInt32 intrinsicState = mContent->IntrinsicState();
+  nsEventStates intrinsicState = mContent->IntrinsicState();
 
-  if (intrinsicState & NS_EVENT_STATE_INVALID)
+  if (intrinsicState.HasState(NS_EVENT_STATE_INVALID))
     *aState |= nsIAccessibleStates::STATE_INVALID;
 
-  if (intrinsicState & NS_EVENT_STATE_REQUIRED)
+  if (intrinsicState.HasState(NS_EVENT_STATE_REQUIRED))
     *aState |= nsIAccessibleStates::STATE_REQUIRED;
 
   PRBool disabled = mContent->IsHTML() ? 
-    (intrinsicState & NS_EVENT_STATE_DISABLED) :
+    (intrinsicState.HasState(NS_EVENT_STATE_DISABLED)) :
     (mContent->AttrValueIs(kNameSpaceID_None,
                            nsAccessibilityAtoms::disabled,
                            nsAccessibilityAtoms::_true,
diff --git a/accessible/src/base/nsDocAccessible.cpp b/accessible/src/base/nsDocAccessible.cpp
index 6acf758a19fb..f3bef44b4664 100644
--- a/accessible/src/base/nsDocAccessible.cpp
+++ b/accessible/src/base/nsDocAccessible.cpp
@@ -1249,9 +1249,9 @@ void nsDocAccessible::ContentAppended(nsIDocument *aDocument,
 void nsDocAccessible::ContentStatesChanged(nsIDocument* aDocument,
                                            nsIContent* aContent1,
                                            nsIContent* aContent2,
-                                           PRInt32 aStateMask)
+                                           nsEventStates aStateMask)
 {
-  if (0 == (aStateMask & NS_EVENT_STATE_CHECKED)) {
+  if (!aStateMask.HasState(NS_EVENT_STATE_CHECKED)) {
     return;
   }
 
@@ -1260,7 +1260,7 @@ void nsDocAccessible::ContentStatesChanged(nsIDocument* aDocument,
 }
 
 void nsDocAccessible::DocumentStatesChanged(nsIDocument* aDocument,
-                                            PRInt32 aStateMask)
+                                            nsEventStates aStateMask)
 {
 }
 
diff --git a/content/base/public/nsIContent.h b/content/base/public/nsIContent.h
index 7943db06d48d..1e5b39800075 100644
--- a/content/base/public/nsIContent.h
+++ b/content/base/public/nsIContent.h
@@ -71,8 +71,8 @@ enum nsLinkState {
 
 // IID for the nsIContent interface
 #define NS_ICONTENT_IID       \
-{ 0x64ef8589, 0xbd19, 0x40f4, \
-  { 0xa9, 0x61, 0x47, 0x89, 0xe0, 0x8d, 0xb0, 0x49 } }
+{ 0x71afb9e6, 0xe8a7, 0x475d, \
+  { 0x89, 0xc4, 0xe4, 0x62, 0x21, 0xeb, 0xe1, 0xa4 } }
 
 /**
  * A node of content in a document's content model. This interface
@@ -787,9 +787,7 @@ public:
    * content state, use nsIEventStateManager.  Also see nsIEventStateManager
    * for the possible bits that could be set here.
    */
-  // XXXbz this is PRInt32 because all the ESM content state APIs use
-  // PRInt32.  We should really use PRUint32 instead.
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   /**
    * Get the ID of this content node (the atom corresponding to the
diff --git a/content/base/public/nsIDocument.h b/content/base/public/nsIDocument.h
index c0a26b4fb5d2..30086c3cd6e5 100644
--- a/content/base/public/nsIDocument.h
+++ b/content/base/public/nsIDocument.h
@@ -65,6 +65,7 @@
 #include "nsIScriptGlobalObject.h"
 #include "nsIDocumentEncoder.h"
 #include "nsIAnimationFrameListener.h"
+#include "nsEventStates.h"
 
 class nsIContent;
 class nsPresContext;
@@ -120,8 +121,8 @@ class Element;
 
 
 #define NS_IDOCUMENT_IID      \
-{ 0x73d79167, 0xacba, 0x46eb, \
-  { 0xad, 0x45, 0xa3, 0x4b, 0x92, 0xf6, 0x01, 0x5b } }
+{ 0x7fb1e97d, 0xbd2c, 0x47cf, \
+  { 0xa3, 0x05, 0x5b, 0x31, 0xd4, 0x1d, 0x3a, 0x52 } }
 
 // Flag for AddStyleSheet().
 #define NS_STYLESHEET_FROM_CATALOG                (1 << 0)
@@ -129,9 +130,9 @@ class Element;
 // Document states
 
 // RTL locale: specific to the XUL localedir attribute
-#define NS_DOCUMENT_STATE_RTL_LOCALE              (1 << 0)
+#define NS_DOCUMENT_STATE_RTL_LOCALE              NS_DEFINE_EVENT_STATE_MACRO(0)
 // Window activation status
-#define NS_DOCUMENT_STATE_WINDOW_INACTIVE         (1 << 1)
+#define NS_DOCUMENT_STATE_WINDOW_INACTIVE         NS_DEFINE_EVENT_STATE_MACRO(1)
 
 //----------------------------------------------------------------------
 
@@ -723,12 +724,12 @@ public:
   // either may be nsnull, but not both
   virtual void ContentStatesChanged(nsIContent* aContent1,
                                     nsIContent* aContent2,
-                                    PRInt32 aStateMask) = 0;
+                                    nsEventStates aStateMask) = 0;
 
   // Notify that a document state has changed.
   // This should only be called by callers whose state is also reflected in the
   // implementation of nsDocument::GetDocumentState.
-  virtual void DocumentStatesChanged(PRInt32 aStateMask) = 0;
+  virtual void DocumentStatesChanged(nsEventStates aStateMask) = 0;
 
   // Observation hooks for style data to propagate notifications
   // to document observers
@@ -1415,7 +1416,7 @@ public:
    * Document state bits have the form NS_DOCUMENT_STATE_* and are declared in
    * nsIDocument.h.
    */
-  virtual PRInt32 GetDocumentState() = 0;
+  virtual nsEventStates GetDocumentState() = 0;
 
   virtual nsISupports* GetCurrentContentSink() = 0;
 
diff --git a/content/base/public/nsIDocumentObserver.h b/content/base/public/nsIDocumentObserver.h
index 32ad4ac97be7..36b1ec2e257a 100644
--- a/content/base/public/nsIDocumentObserver.h
+++ b/content/base/public/nsIDocumentObserver.h
@@ -39,6 +39,7 @@
 
 #include "nsISupports.h"
 #include "nsIMutationObserver.h"
+#include "nsEventStates.h"
 
 class nsIAtom;
 class nsIContent;
@@ -48,8 +49,8 @@ class nsString;
 class nsIDocument;
 
 #define NS_IDOCUMENT_OBSERVER_IID \
-{ 0x4e14e321, 0xa4bb, 0x49f8, \
-  { 0xa5, 0x7a, 0x23, 0x63, 0x66, 0x8d, 0x14, 0xd0 } }
+{ 0x3d005225, 0x210f, 0x4b07, \
+  { 0xb1, 0xd9, 0x96, 0x02, 0x05, 0x74, 0xc4, 0x37 } }
 
 typedef PRUint32 nsUpdateType;
 
@@ -115,7 +116,7 @@ public:
   virtual void ContentStatesChanged(nsIDocument* aDocument,
                                     nsIContent* aContent1,
                                     nsIContent* aContent2,
-                                    PRInt32 aStateMask) = 0;
+                                    nsEventStates aStateMask) = 0;
 
   /**
    * Notification that the state of the document has changed.
@@ -124,7 +125,7 @@ public:
    * @param aStateMask the state that changed
    */
   virtual void DocumentStatesChanged(nsIDocument* aDocument,
-                                     PRInt32 aStateMask) = 0;
+                                     nsEventStates aStateMask) = 0;
 
   /**
    * A StyleSheet has just been added to the document.  This method is
@@ -250,11 +251,11 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsIDocumentObserver, NS_IDOCUMENT_OBSERVER_IID)
     virtual void ContentStatesChanged(nsIDocument* aDocument,                \
                                       nsIContent* aContent1,                 \
                                       nsIContent* aContent2,                 \
-                                      PRInt32 aStateMask);
+                                      nsEventStates aStateMask);
 
 #define NS_DECL_NSIDOCUMENTOBSERVER_DOCUMENTSTATESCHANGED                    \
     virtual void DocumentStatesChanged(nsIDocument* aDocument,               \
-                                       PRInt32 aStateMask);
+                                       nsEventStates aStateMask);
 
 #define NS_DECL_NSIDOCUMENTOBSERVER_STYLESHEETADDED                          \
     virtual void StyleSheetAdded(nsIDocument* aDocument,                     \
@@ -329,13 +330,13 @@ void                                                                      \
 _class::ContentStatesChanged(nsIDocument* aDocument,                      \
                              nsIContent* aContent1,                       \
                              nsIContent* aContent2,                       \
-                             PRInt32 aStateMask)                          \
+                             nsEventStates aStateMask)                    \
 {                                                                         \
 }                                                                         \
                                                                           \
 void                                                                      \
 _class::DocumentStatesChanged(nsIDocument* aDocument,                     \
-                              PRInt32 aStateMask)                         \
+                              nsEventStates aStateMask)                   \
 {                                                                         \
 }
 
diff --git a/content/base/public/nsIImageLoadingContent.idl b/content/base/public/nsIImageLoadingContent.idl
index a9c80b42efbb..e9346ea72ead 100644
--- a/content/base/public/nsIImageLoadingContent.idl
+++ b/content/base/public/nsIImageLoadingContent.idl
@@ -65,7 +65,7 @@ interface nsIDocument;
  * sufficient, when combined with the imageBlockingStatus information.)
  */
 
-[scriptable, uuid(7974082c-3267-4ab1-96fa-bd47d7e3a093)]
+[scriptable, uuid(95c74255-df9a-4060-b5a0-0d111fcafe08)]
 interface nsIImageLoadingContent : imgIDecoderObserver
 {
   /**
@@ -174,7 +174,7 @@ interface nsIImageLoadingContent : imgIDecoderObserver
    * nsImageLoadingContent::ImageState() to return |aState|. Call again with |aForce|
    * as PR_FALSE to revert ImageState() to its original behaviour.
    */
-  void forceImageState(in boolean aForce, in long aState);
+  void forceImageState(in boolean aForce, in unsigned long long aState);
 
   /**
     * We need to be notified when our document changes.
diff --git a/content/base/src/Link.cpp b/content/base/src/Link.cpp
index 043d876e29ae..e88fe8f9e52a 100644
--- a/content/base/src/Link.cpp
+++ b/content/base/src/Link.cpp
@@ -84,7 +84,7 @@ Link::SetLinkState(nsLinkState aState)
                "Setting state to the currently set state!");
 
   // Remember our old link state for when we notify.
-  PRInt32 oldLinkState = LinkState();
+  nsEventStates oldLinkState = LinkState();
 
   // Set our current state as appropriate.
   mLinkState = aState;
@@ -96,7 +96,7 @@ Link::SetLinkState(nsLinkState aState)
   nsIContent *content = Content();
   nsIDocument *doc = content->GetCurrentDoc();
   NS_ASSERTION(doc, "Registered but we have no document?!");
-  PRInt32 newLinkState = LinkState();
+  nsEventStates newLinkState = LinkState();
   NS_ASSERTION(newLinkState == NS_EVENT_STATE_VISITED ||
                newLinkState == NS_EVENT_STATE_UNVISITED,
                "Unexpected state obtained from LinkState()!");
@@ -104,7 +104,7 @@ Link::SetLinkState(nsLinkState aState)
   doc->ContentStatesChanged(content, nsnull, oldLinkState ^ newLinkState);
 }
 
-PRInt32
+nsEventStates
 Link::LinkState() const
 {
   // We are a constant method, but we are just lazily doing things and have to
@@ -124,7 +124,7 @@ Link::LinkState() const
     nsCOMPtr<nsIURI> hrefURI(GetURI());
     if (!hrefURI) {
       self->mLinkState = eLinkState_NotLink;
-      return 0;
+      return nsEventStates();
     }
 
     // We have a good href, so register with History.
@@ -153,7 +153,7 @@ Link::LinkState() const
     return NS_EVENT_STATE_UNVISITED;
   }
 
-  return 0;
+  return nsEventStates();
 }
 
 already_AddRefed<nsIURI>
@@ -491,7 +491,7 @@ Link::ResetLinkState(bool aNotify)
   // not before.  In particular, we need to make sure that our LinkState() is
   // called so that we'll start a new history query as needed.
   if (aNotify && doc) {
-    PRUint32 changedState = NS_EVENT_STATE_VISITED ^ NS_EVENT_STATE_UNVISITED;
+    nsEventStates changedState = NS_EVENT_STATE_VISITED ^ NS_EVENT_STATE_UNVISITED;
     MOZ_AUTO_DOC_UPDATE(doc, UPDATE_STYLE, aNotify);
     doc->ContentStatesChanged(content, nsnull, changedState);
   }
diff --git a/content/base/src/Link.h b/content/base/src/Link.h
index a572a53de748..f72872148d16 100644
--- a/content/base/src/Link.h
+++ b/content/base/src/Link.h
@@ -68,7 +68,7 @@ public:
    *         NS_EVENT_STATE_UNVISTED if this link is not visited, or 0 if this
    *         link is not actually a link.
    */
-  PRInt32 LinkState() const;
+  nsEventStates LinkState() const;
 
   /**
    * @return the URI this link is for, if available.
diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index bd9dc3cb5ebc..1ce43f198ddd 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -4206,14 +4206,14 @@ nsDocument::EndLoad()
 
 void
 nsDocument::ContentStatesChanged(nsIContent* aContent1, nsIContent* aContent2,
-                                 PRInt32 aStateMask)
+                                 nsEventStates aStateMask)
 {
   NS_DOCUMENT_NOTIFY_OBSERVERS(ContentStatesChanged,
                                (this, aContent1, aContent2, aStateMask));
 }
 
 void
-nsDocument::DocumentStatesChanged(PRInt32 aStateMask)
+nsDocument::DocumentStatesChanged(nsEventStates aStateMask)
 {
   // Invalidate our cached state.
   mGotDocumentState &= ~aStateMask;
@@ -7734,16 +7734,16 @@ nsDocument::MaybePreLoadImage(nsIURI* uri)
   }
 }
 
-PRInt32
+nsEventStates
 nsDocument::GetDocumentState()
 {
-  if (!(mGotDocumentState & NS_DOCUMENT_STATE_RTL_LOCALE)) {
+  if (!mGotDocumentState.HasState(NS_DOCUMENT_STATE_RTL_LOCALE)) {
     if (IsDocumentRightToLeft()) {
       mDocumentState |= NS_DOCUMENT_STATE_RTL_LOCALE;
     }
     mGotDocumentState |= NS_DOCUMENT_STATE_RTL_LOCALE;
   }
-  if (!(mGotDocumentState & NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
+  if (!mGotDocumentState.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
     nsIPresShell* shell = GetShell();
     if (shell && shell->GetPresContext() &&
         shell->GetPresContext()->IsTopLevelWindowInactive()) {
diff --git a/content/base/src/nsDocument.h b/content/base/src/nsDocument.h
index 40e6ba625c6d..5e8ed15b39d6 100644
--- a/content/base/src/nsDocument.h
+++ b/content/base/src/nsDocument.h
@@ -710,8 +710,8 @@ public:
 
   virtual void ContentStatesChanged(nsIContent* aContent1,
                                     nsIContent* aContent2,
-                                    PRInt32 aStateMask);
-  virtual void DocumentStatesChanged(PRInt32 aStateMask);
+                                    nsEventStates aStateMask);
+  virtual void DocumentStatesChanged(nsEventStates aStateMask);
 
   virtual void StyleRuleChanged(nsIStyleSheet* aStyleSheet,
                                 nsIStyleRule* aOldStyleRule,
@@ -952,7 +952,7 @@ public:
 
   virtual nsISupports* GetCurrentContentSink();
 
-  virtual PRInt32 GetDocumentState();
+  virtual nsEventStates GetDocumentState();
 
   virtual void RegisterFileDataUri(const nsACString& aUri);
   virtual void UnregisterFileDataUri(const nsACString& aUri);
@@ -1171,8 +1171,8 @@ protected:
 
   nsCOMPtr<nsIContent> mFirstBaseNodeWithHref;
 
-  PRInt32 mDocumentState;
-  PRInt32 mGotDocumentState;
+  nsEventStates mDocumentState;
+  nsEventStates mGotDocumentState;
 
 private:
   friend class nsUnblockOnloadEvent;
diff --git a/content/base/src/nsGenConImageContent.cpp b/content/base/src/nsGenConImageContent.cpp
index c0e126e268bf..801be5590e3f 100644
--- a/content/base/src/nsGenConImageContent.cpp
+++ b/content/base/src/nsGenConImageContent.cpp
@@ -64,7 +64,7 @@ public:
   }
 
   // nsIContent overrides
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   
 private:
   virtual ~nsGenConImageContent();
@@ -96,13 +96,13 @@ nsGenConImageContent::~nsGenConImageContent()
   DestroyImageLoadingContent();
 }
 
-PRInt32
+nsEventStates
 nsGenConImageContent::IntrinsicState() const
 {
-  PRInt32 state = nsXMLElement::IntrinsicState();
+  nsEventStates state = nsXMLElement::IntrinsicState();
 
-  PRInt32 imageState = nsImageLoadingContent::ImageState();
-  if (imageState & (NS_EVENT_STATE_BROKEN | NS_EVENT_STATE_USERDISABLED)) {
+  nsEventStates imageState = nsImageLoadingContent::ImageState();
+  if (imageState.HasAtLeastOneOfStates(NS_EVENT_STATE_BROKEN | NS_EVENT_STATE_USERDISABLED)) {
     // We should never be in an error state; if the image fails to load, we
     // just go to the suppressed state.
     imageState |= NS_EVENT_STATE_SUPPRESSED;
diff --git a/content/base/src/nsGenericElement.cpp b/content/base/src/nsGenericElement.cpp
index 082fa70092da..4f0d6004ca41 100644
--- a/content/base/src/nsGenericElement.cpp
+++ b/content/base/src/nsGenericElement.cpp
@@ -771,7 +771,7 @@ nsINode::LookupNamespaceURI(const nsAString& aNamespacePrefix,
 
 //----------------------------------------------------------------------
 
-PRInt32
+nsEventStates
 nsIContent::IntrinsicState() const
 {
   return IsEditable() ? NS_EVENT_STATE_MOZ_READWRITE :
@@ -4675,9 +4675,9 @@ nsGenericElement::SetAttrAndNotify(PRInt32 aNamespaceID,
 
   // When notifying, make sure to keep track of states whose value
   // depends solely on the value of an attribute.
-  PRUint32 stateMask;
+  nsEventStates stateMask;
   if (aNotify) {
-    stateMask = PRUint32(IntrinsicState());
+    stateMask = IntrinsicState();
   }
 
   nsMutationGuard::DidMutate();
@@ -4712,8 +4712,8 @@ nsGenericElement::SetAttrAndNotify(PRInt32 aNamespaceID,
   }
 
   if (aNotify) {
-    stateMask = stateMask ^ PRUint32(IntrinsicState());
-    if (stateMask && document) {
+    stateMask ^= IntrinsicState();
+    if (document && !stateMask.IsEmpty()) {
       MOZ_AUTO_DOC_UPDATE(document, UPDATE_CONTENT_STATE, aNotify);
       document->ContentStatesChanged(this, nsnull, stateMask);
     }
@@ -4914,10 +4914,10 @@ nsGenericElement::UnsetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
 
   // When notifying, make sure to keep track of states whose value
   // depends solely on the value of an attribute.
-  PRUint32 stateMask;
+  nsEventStates stateMask;
   if (aNotify) {
-    stateMask = PRUint32(IntrinsicState());
-  }    
+    stateMask = IntrinsicState();
+  }
 
   PRBool hasMutationListeners = aNotify &&
     nsContentUtils::HasMutationListeners(this,
@@ -4959,8 +4959,8 @@ nsGenericElement::UnsetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
   }
 
   if (aNotify) {
-    stateMask = stateMask ^ PRUint32(IntrinsicState());
-    if (stateMask && document) {
+    stateMask ^= IntrinsicState();
+    if (document && !stateMask.IsEmpty()) {
       MOZ_AUTO_DOC_UPDATE(document, UPDATE_CONTENT_STATE, aNotify);
       document->ContentStatesChanged(this, nsnull, stateMask);
     }
diff --git a/content/base/src/nsImageLoadingContent.cpp b/content/base/src/nsImageLoadingContent.cpp
index d3be9000cde8..7bdb91d8c1c3 100644
--- a/content/base/src/nsImageLoadingContent.cpp
+++ b/content/base/src/nsImageLoadingContent.cpp
@@ -699,21 +699,36 @@ nsImageLoadingContent::LoadImage(nsIURI* aNewURI,
 }
 
 nsresult
-nsImageLoadingContent::ForceImageState(PRBool aForce, PRInt32 aState)
+nsImageLoadingContent::ForceImageState(PRBool aForce, nsEventStates::InternalType aState)
 {
   mIsImageStateForced = aForce;
-  mForcedImageState = aState;
+  mForcedImageState = nsEventStates(aState);
   return NS_OK;
 }
 
-PRInt32
+nsEventStates
 nsImageLoadingContent::ImageState() const
 {
-  return mIsImageStateForced ? mForcedImageState :
-    (mBroken * NS_EVENT_STATE_BROKEN) |
-    (mUserDisabled * NS_EVENT_STATE_USERDISABLED) |
-    (mSuppressed * NS_EVENT_STATE_SUPPRESSED) |
-    (mLoading * NS_EVENT_STATE_LOADING);
+  if (mIsImageStateForced) {
+    return mForcedImageState;
+  }
+
+  nsEventStates states;
+
+  if (mBroken) {
+    states |= NS_EVENT_STATE_BROKEN;
+  }
+  if (mUserDisabled) {
+    states |= NS_EVENT_STATE_USERDISABLED;
+  }
+  if (mSuppressed) {
+    states |= NS_EVENT_STATE_SUPPRESSED;
+  }
+  if (mLoading) {
+    states |= NS_EVENT_STATE_LOADING;
+  }
+
+  return states;
 }
 
 void
@@ -734,7 +749,7 @@ nsImageLoadingContent::UpdateImageState(PRBool aNotify)
     return;
   }
 
-  PRInt32 oldState = ImageState();
+  nsEventStates oldState = ImageState();
 
   mLoading = mBroken = mUserDisabled = mSuppressed = PR_FALSE;
   
@@ -762,8 +777,8 @@ nsImageLoadingContent::UpdateImageState(PRBool aNotify)
     nsIDocument* doc = thisContent->GetCurrentDoc();
     if (doc) {
       NS_ASSERTION(thisContent->IsInDoc(), "Something is confused");
-      PRInt32 changedBits = oldState ^ ImageState();
-      if (changedBits) {
+      nsEventStates changedBits = oldState ^ ImageState();
+      if (!changedBits.IsEmpty()) {
         mozAutoDocUpdate upd(doc, UPDATE_CONTENT_STATE, PR_TRUE);
         doc->ContentStatesChanged(thisContent, nsnull, changedBits);
       }
diff --git a/content/base/src/nsImageLoadingContent.h b/content/base/src/nsImageLoadingContent.h
index 8e229add0046..a2f2fbebc8a1 100644
--- a/content/base/src/nsImageLoadingContent.h
+++ b/content/base/src/nsImageLoadingContent.h
@@ -96,7 +96,7 @@ protected:
    * be an image (eg an HTML <input> of type other than "image") should just
    * not call this method when computing their intrinsic state.
    */
-  PRInt32 ImageState() const;
+  nsEventStates ImageState() const;
 
   /**
    * LoadImage is called by subclasses when the appropriate
@@ -315,7 +315,7 @@ private:
    * When mIsImageStateForced is true, this holds the ImageState that we'll
    * return in ImageState().
    */
-  PRInt32 mForcedImageState;
+  nsEventStates mForcedImageState;
 
   PRInt16 mImageBlockingStatus;
   PRPackedBool mLoadingEnabled : 1;
diff --git a/content/base/src/nsObjectLoadingContent.cpp b/content/base/src/nsObjectLoadingContent.cpp
index 4bdded1d4e22..72ddee7dd7d3 100644
--- a/content/base/src/nsObjectLoadingContent.cpp
+++ b/content/base/src/nsObjectLoadingContent.cpp
@@ -359,7 +359,7 @@ class AutoNotifier {
     nsObjectLoadingContent*            mContent;
     PRBool                             mNotify;
     nsObjectLoadingContent::ObjectType mOldType;
-    PRInt32                            mOldState;
+    nsEventStates                      mOldState;
 };
 
 /**
@@ -1043,7 +1043,7 @@ nsObjectLoadingContent::AsyncOnChannelRedirect(nsIChannel *aOldChannel,
 }
 
 // <public>
-PRInt32
+nsEventStates
 nsObjectLoadingContent::ObjectState() const
 {
   switch (mType) {
@@ -1056,7 +1056,7 @@ nsObjectLoadingContent::ObjectState() const
       // These are OK. If documents start to load successfully, they display
       // something, and are thus not broken in this sense. The same goes for
       // plugins.
-      return 0;
+      return nsEventStates();
     case eType_Null:
       if (mSuppressed)
         return NS_EVENT_STATE_SUPPRESSED;
@@ -1064,7 +1064,7 @@ nsObjectLoadingContent::ObjectState() const
         return NS_EVENT_STATE_USERDISABLED;
 
       // Otherwise, broken
-      PRInt32 state = NS_EVENT_STATE_BROKEN;
+      nsEventStates state = NS_EVENT_STATE_BROKEN;
       switch (mFallbackReason) {
         case ePluginDisabled:
           state |= NS_EVENT_STATE_HANDLER_DISABLED;
@@ -1083,7 +1083,7 @@ nsObjectLoadingContent::ObjectState() const
   };
   NS_NOTREACHED("unknown type?");
   // this return statement only exists to avoid a compile warning
-  return 0;
+  return nsEventStates();
 }
 
 // <protected>
@@ -1634,11 +1634,11 @@ nsObjectLoadingContent::UnloadContent()
 
 void
 nsObjectLoadingContent::NotifyStateChanged(ObjectType aOldType,
-                                          PRInt32 aOldState,
-                                          PRBool aSync)
+                                          nsEventStates aOldState, PRBool aSync)
 {
-  LOG(("OBJLC [%p]: Notifying about state change: (%u, %x) -> (%u, %x) (sync=%i)\n",
-       this, aOldType, aOldState, mType, ObjectState(), aSync));
+  LOG(("OBJLC [%p]: Notifying about state change: (%u, %lx) -> (%u, %lx) (sync=%i)\n",
+       this, aOldType, aOldState.GetInternalValue(), mType,
+       ObjectState().GetInternalValue(), aSync));
 
   nsCOMPtr<nsIContent> thisContent = 
     do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
@@ -1649,12 +1649,12 @@ nsObjectLoadingContent::NotifyStateChanged(ObjectType aOldType,
     return; // Nothing to do
   }
 
-  PRInt32 newState = ObjectState();
+  nsEventStates newState = ObjectState();
 
   if (newState != aOldState) {
     // This will trigger frame construction
     NS_ASSERTION(thisContent->IsInDoc(), "Something is confused");
-    PRInt32 changedBits = aOldState ^ newState;
+    nsEventStates changedBits = aOldState ^ newState;
 
     {
       mozAutoDocUpdate upd(doc, UPDATE_CONTENT_STATE, PR_TRUE);
diff --git a/content/base/src/nsObjectLoadingContent.h b/content/base/src/nsObjectLoadingContent.h
index 50ba39398158..68559d662dae 100644
--- a/content/base/src/nsObjectLoadingContent.h
+++ b/content/base/src/nsObjectLoadingContent.h
@@ -132,7 +132,7 @@ class nsObjectLoadingContent : public nsImageLoadingContent
      * NS_EVENT_STATE_BROKEN, NS_EVENT_STATE_USERDISABLED and
      * NS_EVENT_STATE_SUPPRESSED representing the current state of the object.
      */
-    PRInt32 ObjectState() const;
+    nsEventStates ObjectState() const;
 
     void SetIsNetworkCreated(PRBool aNetworkCreated)
     {
@@ -259,7 +259,7 @@ class nsObjectLoadingContent : public nsImageLoadingContent
      * @param aSync If a synchronous frame construction is required. If false,
      *              the construction may either be sync or async.
      */
-    void NotifyStateChanged(ObjectType aOldType, PRInt32 aOldState,
+    void NotifyStateChanged(ObjectType aOldType, nsEventStates aOldState,
                             PRBool aSync);
 
     /**
diff --git a/content/events/public/Makefile.in b/content/events/public/Makefile.in
index 2f76e0a18f2f..96dab6511518 100644
--- a/content/events/public/Makefile.in
+++ b/content/events/public/Makefile.in
@@ -55,6 +55,7 @@ EXPORTS		= \
 		nsPLDOMEvent.h \
 		nsEventDispatcher.h \
 		nsPIDOMEventTarget.h \
+		nsEventStates.h \
 		$(NULL)
 
 XPIDLSRCS	= \
diff --git a/content/events/public/nsEventStates.h b/content/events/public/nsEventStates.h
new file mode 100644
index 000000000000..58ff20249a7b
--- /dev/null
+++ b/content/events/public/nsEventStates.h
@@ -0,0 +1,266 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla code.
+ *
+ * The Initial Developer of the Original Code is Mozilla Foundation
+ * Portions created by the Initial Developer are Copyright (C) 2010
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Mounir Lamouri <mounir.lamouri@mozilla.com> (original author)
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either of the GNU General Public License Version 2 or later (the "GPL"),
+ * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsEventStates_h__
+#define nsEventStates_h__
+
+/**
+ * nsEventStates is the class used to represent the event states of nsIContent
+ * instances. These states are calculated by IntrinsicState() and
+ * ContentStatesChanged() has to be called when one of them changes thus
+ * informing the layout/style engine of the change.
+ * Event states are associated with pseudo-classes.
+ */
+class nsEventStates
+{
+public:
+  typedef PRUint64 InternalType;
+
+  nsEventStates()
+    : mStates(0)
+  { }
+
+  // NOTE: the ideal scenario would be to have the default constructor public
+  // setting mStates to 0 and this constructor (without = 0) private.
+  // In that case, we could be sure that only macros at the end were creating
+  // nsEventStates instances with mStates set to something else than 0.
+  // Unfortunately, this constructor is needed at at least two places now.
+  explicit nsEventStates(InternalType aStates)
+    : mStates(aStates)
+  { }
+
+  nsEventStates(const nsEventStates& aEventStates) {
+    mStates = aEventStates.mStates;
+  }
+
+  nsEventStates& operator=(const nsEventStates& aEventStates) {
+    mStates = aEventStates.mStates;
+    return *this;
+  }
+
+  nsEventStates operator|(const nsEventStates& aEventStates) const {
+    return nsEventStates(mStates | aEventStates.mStates);
+  }
+
+  nsEventStates& operator|=(const nsEventStates& aEventStates) {
+    mStates |= aEventStates.mStates;
+    return *this;
+  }
+
+  // NOTE: calling if (eventStates1 & eventStates2) will not build.
+  // This might work correctly if operator bool() is defined
+  // but using HasState, HasAllStates or HasAtLeastOneOfStates is recommended.
+  nsEventStates operator&(const nsEventStates& aEventStates) const {
+    return nsEventStates(mStates & aEventStates.mStates);
+  }
+
+  nsEventStates& operator&=(const nsEventStates& aEventStates) {
+    mStates &= aEventStates.mStates;
+    return *this;
+  }
+
+  bool operator==(const nsEventStates& aEventStates) const {
+    return mStates == aEventStates.mStates;
+  }
+
+  bool operator!=(const nsEventStates& aEventStates) const {
+    return mStates != aEventStates.mStates;
+  }
+
+  nsEventStates operator~() const {
+    return nsEventStates(~mStates);
+  }
+
+  nsEventStates operator^(const nsEventStates& aEventStates) const {
+    return nsEventStates(mStates ^ aEventStates.mStates);
+  }
+
+  nsEventStates& operator^=(const nsEventStates& aEventStates) {
+    mStates ^= aEventStates.mStates;
+    return *this;
+  }
+
+  /**
+   * Returns true if the nsEventStates instance is empty.
+   * A nsEventStates instance is empty if it contains no state.
+   *
+   * @return Whether if the object is empty.
+   */
+  bool IsEmpty() const {
+    return mStates == 0;
+  }
+
+  /**
+   * Returns true if the nsEventStates instance contains the state
+   * contained in aEventStates.
+   * @note aEventStates should contain only one state.
+   *
+   * @param aEventStates The state to check.
+   *
+   * @return Whether the object has the state from aEventStates
+   */
+  bool HasState(nsEventStates aEventStates) const {
+#ifdef DEBUG
+    // If aEventStates.mStates is a power of two, it contains only one state
+    // (or none, but we don't really care).
+    if ((aEventStates.mStates & (aEventStates.mStates - 1))) {
+      NS_ERROR("When calling HasState, "
+               "nsEventStates object has to contain only one state!");
+    }
+#endif // DEBUG
+    return mStates & aEventStates.mStates;
+  }
+
+  /**
+   * Returns true if the nsEventStates instance contains one of the states
+   * contained in aEventStates.
+   *
+   * @param aEventStates The states to check.
+   *
+   * @return Whether the object has at least one state from aEventStates
+   */
+  bool HasAtLeastOneOfStates(nsEventStates aEventStates) const {
+    return mStates & aEventStates.mStates;
+  }
+
+  /**
+   * Returns true if the nsEventStates instance contains all states
+   * contained in aEventStates.
+   *
+   * @param aEventStates The states to check.
+   *
+   * @return Whether the object has all states from aEventStates
+   */
+  bool HasAllStates(nsEventStates aEventStates) const {
+    return (mStates & aEventStates.mStates) == aEventStates.mStates;
+  }
+
+  // We only need that method for inDOMUtils::GetContentState.
+  // If inDOMUtils::GetContentState is removed, this method should be removed.
+  InternalType GetInternalValue() const {
+    return mStates;
+  }
+
+private:
+  InternalType mStates;
+};
+
+/**
+ * The following macros are creating nsEventStates instance with different
+ * values depending of their meaning.
+ * Ideally, nsEventStates instance with values different than 0 should only be
+ * created that way.
+ */
+
+// Helper to define a new nsEventStates macro.
+#define NS_DEFINE_EVENT_STATE_MACRO(_val)               \
+  (nsEventStates(nsEventStates::InternalType(1) << _val))
+
+// Mouse is down on content.
+#define NS_EVENT_STATE_ACTIVE        NS_DEFINE_EVENT_STATE_MACRO(0)
+// Content has focus.
+#define NS_EVENT_STATE_FOCUS         NS_DEFINE_EVENT_STATE_MACRO(1)
+// Mouse is hovering over content.
+#define NS_EVENT_STATE_HOVER         NS_DEFINE_EVENT_STATE_MACRO(2)
+// Drag is hovering over content.
+#define NS_EVENT_STATE_DRAGOVER      NS_DEFINE_EVENT_STATE_MACRO(3)
+// Content is URL's target (ref).
+#define NS_EVENT_STATE_URLTARGET     NS_DEFINE_EVENT_STATE_MACRO(4)
+// Content is checked.
+#define NS_EVENT_STATE_CHECKED       NS_DEFINE_EVENT_STATE_MACRO(5)
+// Content is enabled (and can be disabled).
+#define NS_EVENT_STATE_ENABLED       NS_DEFINE_EVENT_STATE_MACRO(6)
+// Content is disabled.
+#define NS_EVENT_STATE_DISABLED      NS_DEFINE_EVENT_STATE_MACRO(7)
+// Content is required.
+#define NS_EVENT_STATE_REQUIRED      NS_DEFINE_EVENT_STATE_MACRO(8)
+// Content is optional (and can be required).
+#define NS_EVENT_STATE_OPTIONAL      NS_DEFINE_EVENT_STATE_MACRO(9)
+// Link has been visited.
+#define NS_EVENT_STATE_VISITED       NS_DEFINE_EVENT_STATE_MACRO(10)
+// Link hasn't been visited.
+#define NS_EVENT_STATE_UNVISITED     NS_DEFINE_EVENT_STATE_MACRO(11)
+// Content is valid (and can be invalid).
+#define NS_EVENT_STATE_VALID         NS_DEFINE_EVENT_STATE_MACRO(12)
+// Content is invalid.
+#define NS_EVENT_STATE_INVALID       NS_DEFINE_EVENT_STATE_MACRO(13)
+// Content value is in-range (and can be out-of-range).
+#define NS_EVENT_STATE_INRANGE       NS_DEFINE_EVENT_STATE_MACRO(14)
+// Content value is out-of-range.
+#define NS_EVENT_STATE_OUTOFRANGE    NS_DEFINE_EVENT_STATE_MACRO(15)
+// These two are temporary (see bug 302188)
+// Content is read-only.
+#define NS_EVENT_STATE_MOZ_READONLY  NS_DEFINE_EVENT_STATE_MACRO(16)
+// Content is editable.
+#define NS_EVENT_STATE_MOZ_READWRITE NS_DEFINE_EVENT_STATE_MACRO(17)
+// Content is the default one (meaning depends of the context).
+#define NS_EVENT_STATE_DEFAULT       NS_DEFINE_EVENT_STATE_MACRO(18)
+// Content could not be rendered (image/object/etc).
+#define NS_EVENT_STATE_BROKEN        NS_DEFINE_EVENT_STATE_MACRO(19)
+// Content disabled by the user (images turned off, say).
+#define NS_EVENT_STATE_USERDISABLED  NS_DEFINE_EVENT_STATE_MACRO(20)
+// Content suppressed by the user (ad blocking, etc).
+#define NS_EVENT_STATE_SUPPRESSED    NS_DEFINE_EVENT_STATE_MACRO(21)
+// Content is still loading such that there is nothing to show the
+// user (eg an image which hasn't started coming in yet).
+#define NS_EVENT_STATE_LOADING       NS_DEFINE_EVENT_STATE_MACRO(22)
+// Content is of a type that gecko can't handle.
+#define NS_EVENT_STATE_TYPE_UNSUPPORTED NS_DEFINE_EVENT_STATE_MACRO(23)
+#ifdef MOZ_MATHML
+#define NS_EVENT_STATE_INCREMENT_SCRIPT_LEVEL NS_DEFINE_EVENT_STATE_MACRO(24)
+#endif
+// Handler for the content has been blocked.
+#define NS_EVENT_STATE_HANDLER_BLOCKED NS_DEFINE_EVENT_STATE_MACRO(25)
+// Handler for the content has been disabled.
+#define NS_EVENT_STATE_HANDLER_DISABLED NS_DEFINE_EVENT_STATE_MACRO(26)
+// Content is in the indeterminate state.
+#define NS_EVENT_STATE_INDETERMINATE NS_DEFINE_EVENT_STATE_MACRO(27)
+// Handler for the content has crashed
+#define NS_EVENT_STATE_HANDLER_CRASHED NS_DEFINE_EVENT_STATE_MACRO(28)
+// Content has focus and should show a ring.
+#define NS_EVENT_STATE_FOCUSRING     NS_DEFINE_EVENT_STATE_MACRO(29)
+// Content shows its placeholder
+#define NS_EVENT_STATE_MOZ_PLACEHOLDER NS_DEFINE_EVENT_STATE_MACRO(30)
+// Content is a submit control and the form isn't valid.
+#define NS_EVENT_STATE_MOZ_SUBMITINVALID NS_DEFINE_EVENT_STATE_MACRO(31)
+
+/**
+ * NOTE: do not go over 63 without updating nsEventStates::InternalType!
+ */
+
+#endif // nsEventStates_h__
+
diff --git a/content/events/public/nsIEventStateManager.h b/content/events/public/nsIEventStateManager.h
index eaa43947b6f5..d97e01ff97fc 100644
--- a/content/events/public/nsIEventStateManager.h
+++ b/content/events/public/nsIEventStateManager.h
@@ -40,6 +40,7 @@
 
 #include "nsEvent.h"
 #include "nsISupports.h"
+#include "nsEventStates.h"
 
 class nsIContent;
 class nsIDocument;
@@ -53,10 +54,9 @@ class imgIContainer;
 /*
  * Event state manager interface.
  */
-// {92EDD580-062E-4471-ADEB-68329B0EC2E4}
 #define NS_IEVENTSTATEMANAGER_IID \
-{ 0x92edd580, 0x062e, 0x4471, \
-  { 0xad, 0xeb, 0x68, 0x32, 0x9b, 0x0e, 0xc2, 0xe4 } }
+{0x69ab5b16, 0x6690, 0x42fc, \
+  { 0xa9, 0xe5, 0xa3, 0xb4, 0xf8, 0x0f, 0xcb, 0xa6 } }
 
 #define NS_EVENT_NEEDS_FRAME(event) (!NS_IS_ACTIVATION_EVENT(event))
 
@@ -95,8 +95,8 @@ public:
    *                      will pretend that those states are also set on aContent.
    * @return              The content state.
    */
-  virtual PRInt32 GetContentState(nsIContent *aContent,
-                                  PRBool aFollowLabels = PR_FALSE) = 0;
+  virtual nsEventStates GetContentState(nsIContent *aContent,
+                                        PRBool aFollowLabels = PR_FALSE) = 0;
 
   /**
    * Notify that the given NS_EVENT_STATE_* bit has changed for this content.
@@ -110,7 +110,7 @@ public:
    *                  frame reconstructions that may occur, but this does not
    *                  affect the return value.
    */
-  virtual PRBool SetContentState(nsIContent *aContent, PRInt32 aState) = 0;
+  virtual PRBool SetContentState(nsIContent *aContent, nsEventStates aState) = 0;
 
   NS_IMETHOD ContentRemoved(nsIDocument* aDocument, nsIContent* aContent) = 0;
   NS_IMETHOD EventStatusOK(nsGUIEvent* aEvent, PRBool *aOK) = 0;
@@ -161,75 +161,4 @@ public:
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIEventStateManager, NS_IEVENTSTATEMANAGER_IID)
 
-#define NS_EVENT_STATE_ACTIVE        (1 << 0)  // mouse is down on content
-#define NS_EVENT_STATE_FOCUS         (1 << 1)  // content has focus
-#define NS_EVENT_STATE_HOVER         (1 << 2)  // mouse is hovering over content
-#define NS_EVENT_STATE_DRAGOVER      (1 << 3)  // drag  is hovering over content
-#define NS_EVENT_STATE_URLTARGET     (1 << 4)  // content is URL's target (ref)
-
-// The following states are used only for ContentStatesChanged
-
-#define NS_EVENT_STATE_CHECKED       (1 << 5)  // CSS3-Selectors
-#define NS_EVENT_STATE_ENABLED       (1 << 6)  // CSS3-Selectors
-#define NS_EVENT_STATE_DISABLED      (1 << 7)  // CSS3-Selectors
-#define NS_EVENT_STATE_REQUIRED      (1 << 8)  // CSS3-UI
-#define NS_EVENT_STATE_OPTIONAL      (1 << 9)  // CSS3-UI
-#define NS_EVENT_STATE_VISITED       (1 << 10) // CSS2
-#define NS_EVENT_STATE_UNVISITED     (1 << 11)
-#define NS_EVENT_STATE_VALID         (1 << 12) // CSS3-UI
-#define NS_EVENT_STATE_INVALID       (1 << 13) // CSS3-UI
-#define NS_EVENT_STATE_INRANGE       (1 << 14) // CSS3-UI
-#define NS_EVENT_STATE_OUTOFRANGE    (1 << 15) // CSS3-UI
-// these two are temporary (see bug 302188)
-#define NS_EVENT_STATE_MOZ_READONLY  (1 << 16) // CSS3-UI
-#define NS_EVENT_STATE_MOZ_READWRITE (1 << 17) // CSS3-UI
-#define NS_EVENT_STATE_DEFAULT       (1 << 18) // CSS3-UI
-
-// Content could not be rendered (image/object/etc).
-#define NS_EVENT_STATE_BROKEN        (1 << 19)
-// Content disabled by the user (images turned off, say)
-#define NS_EVENT_STATE_USERDISABLED  (1 << 20)
-// Content suppressed by the user (ad blocking, etc)
-#define NS_EVENT_STATE_SUPPRESSED    (1 << 21)
-// Content is still loading such that there is nothing to show the
-// user (eg an image which hasn't started coming in yet)
-#define NS_EVENT_STATE_LOADING       (1 << 22)
-// Content is of a type that gecko can't handle
-#define NS_EVENT_STATE_TYPE_UNSUPPORTED \
-                                     (1 << 23)
-#ifdef MOZ_MATHML
-#define NS_EVENT_STATE_INCREMENT_SCRIPT_LEVEL \
-                                     (1 << 24)
-#endif
-// Handler for the content has been blocked
-#define NS_EVENT_STATE_HANDLER_BLOCKED \
-                                     (1 << 25)
-// Handler for the content has been disabled
-#define NS_EVENT_STATE_HANDLER_DISABLED \
-                                     (1 << 26)
-
-#define NS_EVENT_STATE_INDETERMINATE (1 << 27) // CSS3-Selectors
-
-// Handler for the content has crashed
-#define NS_EVENT_STATE_HANDLER_CRASHED \
-                                     (1 << 28)
-
-// content has focus and should show a ring
-#define NS_EVENT_STATE_FOCUSRING     (1 << 29)
-
-// Content shows its placeholder
-#define NS_EVENT_STATE_MOZ_PLACEHOLDER (1 << 30)
-
-// Content is a submit control and the form isn't valid.
-#define NS_EVENT_STATE_MOZ_SUBMITINVALID (1U << 31)
-
-/**
- * WARNING:
- * (1U << 31) should work but we currently handle event states with PRInt32
- * so it's an edge case.
- * DO NOT ADD AN EVENT STATE after NS_EVENT_STATE_MOZ_SUBMITINVALID until we
- * move to PRUint64 and we introduce a type to handle event states.
- * See bug 595036.
- */
-
 #endif // nsIEventStateManager_h__
diff --git a/content/events/src/nsEventStateManager.cpp b/content/events/src/nsEventStateManager.cpp
index e29dd71219f0..6247a8ad0f9d 100644
--- a/content/events/src/nsEventStateManager.cpp
+++ b/content/events/src/nsEventStateManager.cpp
@@ -4159,10 +4159,10 @@ IsAncestorOf(nsIContent* aPossibleAncestor, nsIContent* aPossibleDescendant,
   return false;
 }
 
-PRInt32
+nsEventStates
 nsEventStateManager::GetContentState(nsIContent *aContent, PRBool aFollowLabels)
 {
-  PRInt32 state = aContent->IntrinsicState();
+  nsEventStates state = aContent->IntrinsicState();
 
   if (IsAncestorOf(aContent, mActiveContent, aFollowLabels)) {
     state |= NS_EVENT_STATE_ACTIVE;
@@ -4239,7 +4239,7 @@ static nsIContent* FindCommonAncestor(nsIContent *aNode1, nsIContent *aNode2)
 
 static void
 NotifyAncestors(nsIDocument* aDocument, nsIContent* aStartNode,
-                nsIContent* aStopBefore, PRInt32 aState)
+                nsIContent* aStopBefore, nsEventStates aState)
 {
   while (aStartNode && aStartNode != aStopBefore) {
     aDocument->ContentStatesChanged(aStartNode, nsnull, aState);
@@ -4252,7 +4252,7 @@ NotifyAncestors(nsIDocument* aDocument, nsIContent* aStartNode,
 }
 
 PRBool
-nsEventStateManager::SetContentState(nsIContent *aContent, PRInt32 aState)
+nsEventStateManager::SetContentState(nsIContent *aContent, nsEventStates aState)
 {
   const PRInt32 maxNotify = 5;
   // We must initialize this array with memset for the sake of the boneheaded
@@ -4270,20 +4270,20 @@ nsEventStateManager::SetContentState(nsIContent *aContent, PRInt32 aState)
       return PR_FALSE;
   }
 
-  if ((aState & NS_EVENT_STATE_DRAGOVER) && (aContent != mDragOverContent)) {
+  if (aState.HasState(NS_EVENT_STATE_DRAGOVER) && aContent != mDragOverContent) {
     notifyContent[3] = mDragOverContent; // notify dragover first, since more common case
     NS_IF_ADDREF(notifyContent[3]);
     mDragOverContent = aContent;
   }
 
-  if ((aState & NS_EVENT_STATE_URLTARGET) && (aContent != mURLTargetContent)) {
+  if (aState.HasState(NS_EVENT_STATE_URLTARGET) && aContent != mURLTargetContent) {
     notifyContent[4] = mURLTargetContent;
     NS_IF_ADDREF(notifyContent[4]);
     mURLTargetContent = aContent;
   }
 
   nsCOMPtr<nsIContent> commonActiveAncestor, oldActive, newActive;
-  if ((aState & NS_EVENT_STATE_ACTIVE) && (aContent != mActiveContent)) {
+  if (aState.HasState(NS_EVENT_STATE_ACTIVE) && aContent != mActiveContent) {
     oldActive = mActiveContent;
     newActive = aContent;
     commonActiveAncestor = FindCommonAncestor(mActiveContent, aContent);
@@ -4291,7 +4291,7 @@ nsEventStateManager::SetContentState(nsIContent *aContent, PRInt32 aState)
   }
 
   nsCOMPtr<nsIContent> commonHoverAncestor, oldHover, newHover;
-  if ((aState & NS_EVENT_STATE_HOVER) && (aContent != mHoverContent)) {
+  if (aState.HasState(NS_EVENT_STATE_HOVER) && aContent != mHoverContent) {
     oldHover = mHoverContent;
 
     if (!mPresContext || mPresContext->IsDynamic()) {
@@ -4315,15 +4315,16 @@ nsEventStateManager::SetContentState(nsIContent *aContent, PRInt32 aState)
     mHoverContent = aContent;
   }
 
-  if (aState & NS_EVENT_STATE_FOCUS) {
+  if (aState.HasState(NS_EVENT_STATE_FOCUS)) {
     aState |= NS_EVENT_STATE_FOCUSRING;
     notifyContent[2] = aContent;
     NS_IF_ADDREF(notifyContent[2]);
   }
 
-  PRInt32 simpleStates = aState & ~(NS_EVENT_STATE_ACTIVE|NS_EVENT_STATE_HOVER);
+  nsEventStates simpleStates = aState;
+  simpleStates &= ~(NS_EVENT_STATE_ACTIVE|NS_EVENT_STATE_HOVER);
 
-  if (aContent && simpleStates != 0) {
+  if (aContent && !simpleStates.IsEmpty()) {
     // notify about new content too
     notifyContent[0] = aContent;
     NS_ADDREF(aContent);  // everything in notify array has a ref
diff --git a/content/events/src/nsEventStateManager.h b/content/events/src/nsEventStateManager.h
index f2b1b6ebb6fb..564f6862744c 100644
--- a/content/events/src/nsEventStateManager.h
+++ b/content/events/src/nsEventStateManager.h
@@ -118,9 +118,9 @@ public:
   NS_IMETHOD GetEventTarget(nsIFrame **aFrame);
   NS_IMETHOD GetEventTargetContent(nsEvent* aEvent, nsIContent** aContent);
 
-  virtual PRInt32 GetContentState(nsIContent *aContent,
-                                  PRBool aFollowLabels = PR_FALSE);
-  virtual PRBool SetContentState(nsIContent *aContent, PRInt32 aState);
+  virtual nsEventStates GetContentState(nsIContent *aContent,
+                                        PRBool aFollowLabels = PR_FALSE);
+  virtual PRBool SetContentState(nsIContent *aContent, nsEventStates aState);
   NS_IMETHOD ContentRemoved(nsIDocument* aDocument, nsIContent* aContent);
   NS_IMETHOD EventStatusOK(nsGUIEvent* aEvent, PRBool *aOK);
 
diff --git a/content/html/content/src/nsGenericHTMLElement.cpp b/content/html/content/src/nsGenericHTMLElement.cpp
index 889a3186e2c1..2a169e30eb1c 100644
--- a/content/html/content/src/nsGenericHTMLElement.cpp
+++ b/content/html/content/src/nsGenericHTMLElement.cpp
@@ -2730,13 +2730,13 @@ nsGenericHTMLFormElement::IsSubmittableControl() const
          type & NS_FORM_INPUT_ELEMENT;
 }
 
-PRInt32
+nsEventStates
 nsGenericHTMLFormElement::IntrinsicState() const
 {
   // If you add attribute-dependent states here, you need to add them them to
   // AfterSetAttr too.  And add them to AfterSetAttr for all subclasses that
   // implement IntrinsicState() and are affected by that attribute.
-  PRInt32 state = nsGenericHTMLElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLElement::IntrinsicState();
 
   if (CanBeDisabled()) {
     // :enabled/:disabled
@@ -2949,7 +2949,7 @@ nsGenericHTMLFormElement::UpdateFieldSet()
 }
 
 void
-nsGenericHTMLFormElement::FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify)
+nsGenericHTMLFormElement::FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify)
 {
   if (!aNotify) {
     return;
@@ -3457,7 +3457,7 @@ nsGenericHTMLElement::IsEditableRoot() const
 static void
 MakeContentDescendantsEditable(nsIContent *aContent, nsIDocument *aDocument)
 {
-  PRInt32 stateBefore = aContent->IntrinsicState();
+  nsEventStates stateBefore = aContent->IntrinsicState();
 
   aContent->UpdateEditableState();
 
diff --git a/content/html/content/src/nsGenericHTMLElement.h b/content/html/content/src/nsGenericHTMLElement.h
index dadff607a523..ec04135b323b 100644
--- a/content/html/content/src/nsGenericHTMLElement.h
+++ b/content/html/content/src/nsGenericHTMLElement.h
@@ -846,7 +846,7 @@ public:
   virtual void UnbindFromTree(PRBool aDeep = PR_TRUE,
                               PRBool aNullParent = PR_TRUE);
   virtual PRUint32 GetDesiredIMEState();
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual nsresult PreHandleEvent(nsEventChainPreVisitor& aVisitor);
 
@@ -864,14 +864,14 @@ public:
    * @note Classes redefining this method should not call ContentStatesChanged
    * but they should pass aStates instead.
    */
-  virtual void FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify);
+  virtual void FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify);
 
   void FieldSetFirstLegendChanged(PRBool aNotify) {
     UpdateFieldSet();
 
     // The disabled state may have change because the element might not be in
     // the first legend anymore.
-    FieldSetDisabledChanged(0, aNotify);
+    FieldSetDisabledChanged(nsEventStates(), aNotify);
   }
 
   /**
diff --git a/content/html/content/src/nsHTMLAnchorElement.cpp b/content/html/content/src/nsHTMLAnchorElement.cpp
index 43174dac68a2..6331126d40b9 100644
--- a/content/html/content/src/nsHTMLAnchorElement.cpp
+++ b/content/html/content/src/nsHTMLAnchorElement.cpp
@@ -119,7 +119,7 @@ public:
 
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual nsXPCClassInfo* GetClassInfo();
 };
@@ -479,7 +479,7 @@ nsHTMLAnchorElement::ParseAttribute(PRInt32 aNamespaceID,
                                               aResult);
 }
 
-PRInt32
+nsEventStates
 nsHTMLAnchorElement::IntrinsicState() const
 {
   return Link::LinkState() | nsGenericHTMLElement::IntrinsicState();
diff --git a/content/html/content/src/nsHTMLAreaElement.cpp b/content/html/content/src/nsHTMLAreaElement.cpp
index 1c42ef4b1c9c..3521117f62da 100644
--- a/content/html/content/src/nsHTMLAreaElement.cpp
+++ b/content/html/content/src/nsHTMLAreaElement.cpp
@@ -103,7 +103,7 @@ public:
 
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual nsXPCClassInfo* GetClassInfo();
 };
@@ -331,7 +331,7 @@ nsHTMLAreaElement::GetHrefURI() const
   return GetHrefURIForAnchors();
 }
 
-PRInt32
+nsEventStates
 nsHTMLAreaElement::IntrinsicState() const
 {
   return Link::LinkState() | nsGenericHTMLElement::IntrinsicState();
diff --git a/content/html/content/src/nsHTMLButtonElement.cpp b/content/html/content/src/nsHTMLButtonElement.cpp
index a078f91da10b..0ceda24db769 100644
--- a/content/html/content/src/nsHTMLButtonElement.cpp
+++ b/content/html/content/src/nsHTMLButtonElement.cpp
@@ -110,9 +110,9 @@ public:
   NS_IMETHOD SaveState();
   PRBool RestoreState(nsPresState* aState);
 
-  virtual void FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify);
+  virtual void FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify);
 
-  PRInt32 IntrinsicState() const;
+  nsEventStates IntrinsicState() const;
 
   virtual nsresult BindToTree(nsIDocument* aDocument, nsIContent* aParent,
                                nsIContent* aBindingParent,
@@ -639,7 +639,7 @@ nsresult
 nsHTMLButtonElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
                                   const nsAString* aValue, PRBool aNotify)
 {
-  PRInt32 states = 0;
+  nsEventStates states;
 
   if (aNameSpaceID == kNameSpaceID_None) {
     if (aName == nsGkAtoms::type) {
@@ -655,7 +655,7 @@ nsHTMLButtonElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
       states |= NS_EVENT_STATE_VALID | NS_EVENT_STATE_INVALID;
     }
 
-    if (aNotify && states) {
+    if (aNotify && !states.IsEmpty()) {
       nsIDocument* doc = GetCurrentDoc();
       if (doc) {
         MOZ_AUTO_DOC_UPDATE(doc, UPDATE_CONTENT_STATE, PR_TRUE);
@@ -696,10 +696,10 @@ nsHTMLButtonElement::RestoreState(nsPresState* aState)
   return PR_FALSE;
 }
 
-PRInt32
+nsEventStates
 nsHTMLButtonElement::IntrinsicState() const
 {
-  PRInt32 state = nsGenericHTMLFormElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLFormElement::IntrinsicState();
 
   if (IsCandidateForConstraintValidation()) {
     state |= IsValid() ? NS_EVENT_STATE_VALID : NS_EVENT_STATE_INVALID;
@@ -738,7 +738,7 @@ nsHTMLButtonElement::UpdateBarredFromConstraintValidation()
 }
 
 void
-nsHTMLButtonElement::FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify)
+nsHTMLButtonElement::FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify)
 {
   UpdateBarredFromConstraintValidation();
 
diff --git a/content/html/content/src/nsHTMLFieldSetElement.cpp b/content/html/content/src/nsHTMLFieldSetElement.cpp
index 620e73651bee..5e396ce12f79 100644
--- a/content/html/content/src/nsHTMLFieldSetElement.cpp
+++ b/content/html/content/src/nsHTMLFieldSetElement.cpp
@@ -122,7 +122,7 @@ nsHTMLFieldSetElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
     PRUint32 length = mElements->Length(PR_TRUE);
     for (PRUint32 i=0; i<length; ++i) {
       static_cast<nsGenericHTMLFormElement*>(mElements->GetNodeAt(i))
-        ->FieldSetDisabledChanged(0, aNotify);
+        ->FieldSetDisabledChanged(nsEventStates(), aNotify);
     }
   }
 
diff --git a/content/html/content/src/nsHTMLImageElement.cpp b/content/html/content/src/nsHTMLImageElement.cpp
index 5f653ba1d90d..ba7d1880de75 100644
--- a/content/html/content/src/nsHTMLImageElement.cpp
+++ b/content/html/content/src/nsHTMLImageElement.cpp
@@ -140,7 +140,7 @@ public:
                               nsIContent* aBindingParent,
                               PRBool aCompileEventHandlers);
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
   nsresult CopyInnerTo(nsGenericElement* aDest) const;
@@ -583,7 +583,7 @@ nsHTMLImageElement::MaybeLoadImage()
   }
 }
 
-PRInt32
+nsEventStates
 nsHTMLImageElement::IntrinsicState() const
 {
   return nsGenericHTMLElement::IntrinsicState() |
diff --git a/content/html/content/src/nsHTMLInputElement.cpp b/content/html/content/src/nsHTMLInputElement.cpp
index 84bd822a045c..b626f8109f8e 100644
--- a/content/html/content/src/nsHTMLInputElement.cpp
+++ b/content/html/content/src/nsHTMLInputElement.cpp
@@ -799,7 +799,7 @@ nsHTMLInputElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
                                  PRBool aNotify)
 {
   // States changes that have to be passed to ContentStatesChanged().
-  PRInt32 states = 0;
+  nsEventStates states;
 
   if (aNameSpaceID == kNameSpaceID_None) {
     //
@@ -932,7 +932,7 @@ nsHTMLInputElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
         states |= NS_EVENT_STATE_MOZ_READONLY | NS_EVENT_STATE_MOZ_READWRITE;
       }
 
-      if (doc && states) {
+      if (doc && !states.IsEmpty()) {
         MOZ_AUTO_DOC_UPDATE(doc, UPDATE_CONTENT_STATE, PR_TRUE);
         doc->ContentStatesChanged(this, nsnull, states);
       }
@@ -3257,13 +3257,13 @@ nsHTMLInputElement::DoneCreatingElement()
   SET_BOOLBIT(mBitField, BF_SHOULD_INIT_CHECKED, PR_FALSE);
 }
 
-PRInt32
+nsEventStates
 nsHTMLInputElement::IntrinsicState() const
 {
   // If you add states here, and they're type-dependent, you need to add them
   // to the type case in AfterSetAttr.
   
-  PRInt32 state = nsGenericHTMLFormElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLFormElement::IntrinsicState();
   if (mType == NS_FORM_INPUT_CHECKBOX || mType == NS_FORM_INPUT_RADIO) {
     // Check current checked state (:checked)
     if (GET_BOOLBIT(mBitField, BF_CHECKED)) {
@@ -4413,7 +4413,7 @@ nsHTMLInputElement::OnValueChanged(PRBool aNotify)
 }
 
 void
-nsHTMLInputElement::FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify)
+nsHTMLInputElement::FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify)
 {
   UpdateValueMissingValidityState();
   UpdateBarredFromConstraintValidation();
diff --git a/content/html/content/src/nsHTMLInputElement.h b/content/html/content/src/nsHTMLInputElement.h
index d86afb3e1620..52bde41c1126 100644
--- a/content/html/content/src/nsHTMLInputElement.h
+++ b/content/html/content/src/nsHTMLInputElement.h
@@ -159,7 +159,7 @@ public:
   virtual PRBool RestoreState(nsPresState* aState);
   virtual PRBool AllowDrop();
 
-  virtual void FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify);
+  virtual void FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify);
 
   // nsIContent
   virtual PRBool IsHTMLFocusable(PRBool aWithMouse, PRBool *aIsFocusable, PRInt32 *aTabIndex);
@@ -184,7 +184,7 @@ public:
 
   virtual void DoneCreatingElement();
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   // nsITextControlElement
   NS_IMETHOD SetValueChanged(PRBool aValueChanged);
diff --git a/content/html/content/src/nsHTMLLinkElement.cpp b/content/html/content/src/nsHTMLLinkElement.cpp
index 5bdb3e5157db..92f5cc2d933f 100644
--- a/content/html/content/src/nsHTMLLinkElement.cpp
+++ b/content/html/content/src/nsHTMLLinkElement.cpp
@@ -117,7 +117,7 @@ public:
 
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual nsXPCClassInfo* GetClassInfo();
 protected:
@@ -444,7 +444,7 @@ nsHTMLLinkElement::GetStyleSheetInfo(nsAString& aTitle,
   return;
 }
 
-PRInt32
+nsEventStates
 nsHTMLLinkElement::IntrinsicState() const
 {
   return Link::LinkState() | nsGenericHTMLElement::IntrinsicState();
diff --git a/content/html/content/src/nsHTMLObjectElement.cpp b/content/html/content/src/nsHTMLObjectElement.cpp
index 54356a8eb916..37ed6ae587e0 100644
--- a/content/html/content/src/nsHTMLObjectElement.cpp
+++ b/content/html/content/src/nsHTMLObjectElement.cpp
@@ -122,7 +122,7 @@ public:
                                 nsAttrValue &aResult);
   virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction() const;
   NS_IMETHOD_(PRBool) IsAttributeMapped(const nsIAtom *aAttribute) const;
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   virtual void DestroyContent();
 
   // nsObjectLoadingContent
@@ -524,7 +524,7 @@ nsHTMLObjectElement::StartObjectLoad(PRBool aNotify)
   SetIsNetworkCreated(PR_FALSE);
 }
 
-PRInt32
+nsEventStates
 nsHTMLObjectElement::IntrinsicState() const
 {
   return nsGenericHTMLFormElement::IntrinsicState() | ObjectState();
diff --git a/content/html/content/src/nsHTMLOptGroupElement.cpp b/content/html/content/src/nsHTMLOptGroupElement.cpp
index 59ea1061a892..9e7d68bf31d7 100644
--- a/content/html/content/src/nsHTMLOptGroupElement.cpp
+++ b/content/html/content/src/nsHTMLOptGroupElement.cpp
@@ -82,7 +82,7 @@ public:
   // nsIContent
   virtual nsresult PreHandleEvent(nsEventChainPreVisitor& aVisitor);
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
  
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
@@ -194,10 +194,10 @@ nsHTMLOptGroupElement::RemoveChildAt(PRUint32 aIndex, PRBool aNotify, PRBool aMu
   return rv;
 }
 
-PRInt32
+nsEventStates
 nsHTMLOptGroupElement::IntrinsicState() const
 {
-  PRInt32 state = nsGenericHTMLElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLElement::IntrinsicState();
 
   if (HasAttr(kNameSpaceID_None, nsGkAtoms::disabled)) {
     state |= NS_EVENT_STATE_DISABLED;
diff --git a/content/html/content/src/nsHTMLOptionElement.cpp b/content/html/content/src/nsHTMLOptionElement.cpp
index 3b94ccedb061..8881caa677c3 100644
--- a/content/html/content/src/nsHTMLOptionElement.cpp
+++ b/content/html/content/src/nsHTMLOptionElement.cpp
@@ -338,10 +338,10 @@ nsHTMLOptionElement::SetText(const nsAString& aText)
   return nsContentUtils::SetNodeTextContent(this, aText, PR_TRUE);
 }
 
-PRInt32
+nsEventStates
 nsHTMLOptionElement::IntrinsicState() const
 {
-  PRInt32 state = nsGenericHTMLElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLElement::IntrinsicState();
   // Nasty hack because we need to call an interface method, and one that
   // toggles some of our hidden internal state at that!  Would that we could
   // use |mutable|.
diff --git a/content/html/content/src/nsHTMLOptionElement.h b/content/html/content/src/nsHTMLOptionElement.h
index dd1bdbae9d07..9ce6c8a90f8c 100644
--- a/content/html/content/src/nsHTMLOptionElement.h
+++ b/content/html/content/src/nsHTMLOptionElement.h
@@ -91,7 +91,7 @@ public:
   void SetSelectedInternal(PRBool aValue, PRBool aNotify);
 
   // nsIContent
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
diff --git a/content/html/content/src/nsHTMLSelectElement.cpp b/content/html/content/src/nsHTMLSelectElement.cpp
index 9641bb09fb96..e944e1159663 100644
--- a/content/html/content/src/nsHTMLSelectElement.cpp
+++ b/content/html/content/src/nsHTMLSelectElement.cpp
@@ -1490,10 +1490,10 @@ nsHTMLSelectElement::PreHandleEvent(nsEventChainPreVisitor& aVisitor)
   return nsGenericHTMLFormElement::PreHandleEvent(aVisitor);
 }
 
-PRInt32
+nsEventStates
 nsHTMLSelectElement::IntrinsicState() const
 {
-  PRInt32 state = nsGenericHTMLFormElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLFormElement::IntrinsicState();
 
   if (IsCandidateForConstraintValidation()) {
     state |= IsValid() ? NS_EVENT_STATE_VALID : NS_EVENT_STATE_INVALID;
@@ -2098,7 +2098,7 @@ nsHTMLSelectElement::UpdateBarredFromConstraintValidation()
 }
 
 void
-nsHTMLSelectElement::FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify)
+nsHTMLSelectElement::FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify)
 {
   UpdateBarredFromConstraintValidation();
 
diff --git a/content/html/content/src/nsHTMLSelectElement.h b/content/html/content/src/nsHTMLSelectElement.h
index d45152f4c4ca..51b9fec51829 100644
--- a/content/html/content/src/nsHTMLSelectElement.h
+++ b/content/html/content/src/nsHTMLSelectElement.h
@@ -277,9 +277,9 @@ public:
   NS_IMETHOD SaveState();
   virtual PRBool RestoreState(nsPresState* aState);
 
-  virtual void FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify);
+  virtual void FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify);
 
-  PRInt32 IntrinsicState() const;
+  nsEventStates IntrinsicState() const;
 
   // nsISelectElement
   NS_DECL_NSISELECTELEMENT
diff --git a/content/html/content/src/nsHTMLSharedObjectElement.cpp b/content/html/content/src/nsHTMLSharedObjectElement.cpp
index 2cec057e80db..a113ffcfc6ff 100644
--- a/content/html/content/src/nsHTMLSharedObjectElement.cpp
+++ b/content/html/content/src/nsHTMLSharedObjectElement.cpp
@@ -122,7 +122,7 @@ public:
                                 nsAttrValue &aResult);
   virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction() const;
   NS_IMETHOD_(PRBool) IsAttributeMapped(const nsIAtom *aAttribute) const;
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   virtual void DestroyContent();
 
   // nsObjectLoadingContent
@@ -455,7 +455,7 @@ nsHTMLSharedObjectElement::StartObjectLoad(PRBool aNotify)
   }
 }
 
-PRInt32
+nsEventStates
 nsHTMLSharedObjectElement::IntrinsicState() const
 {
   return nsGenericHTMLElement::IntrinsicState() | ObjectState();
diff --git a/content/html/content/src/nsHTMLTextAreaElement.cpp b/content/html/content/src/nsHTMLTextAreaElement.cpp
index 978daddbc18e..6f5c5d08fe90 100644
--- a/content/html/content/src/nsHTMLTextAreaElement.cpp
+++ b/content/html/content/src/nsHTMLTextAreaElement.cpp
@@ -131,9 +131,9 @@ public:
   NS_IMETHOD SaveState();
   virtual PRBool RestoreState(nsPresState* aState);
 
-  virtual void FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify);
+  virtual void FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify);
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   // nsITextControlElemet
   NS_IMETHOD SetValueChanged(PRBool aValueChanged);
@@ -989,10 +989,10 @@ nsHTMLTextAreaElement::RestoreState(nsPresState* aState)
   return PR_FALSE;
 }
 
-PRInt32
+nsEventStates
 nsHTMLTextAreaElement::IntrinsicState() const
 {
-  PRInt32 state = nsGenericHTMLFormElement::IntrinsicState();
+  nsEventStates state = nsGenericHTMLFormElement::IntrinsicState();
 
   if (HasAttr(kNameSpaceID_None, nsGkAtoms::required)) {
     state |= NS_EVENT_STATE_REQUIRED;
@@ -1109,7 +1109,7 @@ nsresult
 nsHTMLTextAreaElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
                                     const nsAString* aValue, PRBool aNotify)
 {
-  PRInt32 states = 0;
+  nsEventStates states;
 
   if (aNameSpaceID == kNameSpaceID_None) {
     if (aName == nsGkAtoms::required || aName == nsGkAtoms::disabled ||
@@ -1136,7 +1136,7 @@ nsHTMLTextAreaElement::AfterSetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
         states |= NS_EVENT_STATE_MOZ_READONLY | NS_EVENT_STATE_MOZ_READWRITE;
       }
 
-      if (doc && states) {
+      if (doc && !states.IsEmpty()) {
         MOZ_AUTO_DOC_UPDATE(doc, UPDATE_CONTENT_STATE, PR_TRUE);
         doc->ContentStatesChanged(this, nsnull, states);
       }
@@ -1405,7 +1405,7 @@ nsHTMLTextAreaElement::OnValueChanged(PRBool aNotify)
 }
 
 void
-nsHTMLTextAreaElement::FieldSetDisabledChanged(PRInt32 aStates, PRBool aNotify)
+nsHTMLTextAreaElement::FieldSetDisabledChanged(nsEventStates aStates, PRBool aNotify)
 {
   UpdateValueMissingValidityState();
   UpdateBarredFromConstraintValidation();
diff --git a/content/mathml/content/src/nsMathMLElement.cpp b/content/mathml/content/src/nsMathMLElement.cpp
index 6fa144a8b862..3b66e302b2f2 100644
--- a/content/mathml/content/src/nsMathMLElement.cpp
+++ b/content/mathml/content/src/nsMathMLElement.cpp
@@ -436,11 +436,11 @@ nsMathMLElement::MapMathMLAttributesInto(const nsMappedAttributes* aAttributes,
 
 NS_IMPL_ELEMENT_CLONE(nsMathMLElement)
 
-PRInt32
+nsEventStates
 nsMathMLElement::IntrinsicState() const
 {
   return nsMathMLElementBase::IntrinsicState() |
-    (mIncrementScriptLevel ? NS_EVENT_STATE_INCREMENT_SCRIPT_LEVEL : 0);
+    (mIncrementScriptLevel ? NS_EVENT_STATE_INCREMENT_SCRIPT_LEVEL : nsEventStates());
 }
 
 PRBool
diff --git a/content/mathml/content/src/nsMathMLElement.h b/content/mathml/content/src/nsMathMLElement.h
index 9274c69d73df..92058f4da124 100644
--- a/content/mathml/content/src/nsMathMLElement.h
+++ b/content/mathml/content/src/nsMathMLElement.h
@@ -90,7 +90,7 @@ public:
                                       nsRuleData* aRuleData);
   
   nsresult Clone(nsINodeInfo*, nsINode**) const;
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   virtual PRBool IsNodeOfType(PRUint32 aFlags) const;
 
   // Set during reflow as necessary. Does a style change notification,
diff --git a/content/svg/content/src/nsSVGAElement.cpp b/content/svg/content/src/nsSVGAElement.cpp
index fb38eaaa6acc..53f9fa2edc4a 100644
--- a/content/svg/content/src/nsSVGAElement.cpp
+++ b/content/svg/content/src/nsSVGAElement.cpp
@@ -276,7 +276,7 @@ nsSVGAElement::GetLinkTarget(nsAString& aTarget)
   }
 }
 
-PRInt32
+nsEventStates
 nsSVGAElement::IntrinsicState() const
 {
   return Link::LinkState() | nsSVGAElementBase::IntrinsicState();
diff --git a/content/svg/content/src/nsSVGAElement.h b/content/svg/content/src/nsSVGAElement.h
index bf49b01efe34..3d32149f1e90 100644
--- a/content/svg/content/src/nsSVGAElement.h
+++ b/content/svg/content/src/nsSVGAElement.h
@@ -92,7 +92,7 @@ public:
   virtual void GetLinkTarget(nsAString& aTarget);
   virtual nsLinkState GetLinkState() const;
   virtual already_AddRefed<nsIURI> GetHrefURI() const;
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
   nsresult SetAttr(PRInt32 aNameSpaceID, nsIAtom* aName,
                    const nsAString& aValue, PRBool aNotify)
   {
diff --git a/content/svg/content/src/nsSVGFilters.cpp b/content/svg/content/src/nsSVGFilters.cpp
index 8172ab52decd..1fcbcdfc3837 100644
--- a/content/svg/content/src/nsSVGFilters.cpp
+++ b/content/svg/content/src/nsSVGFilters.cpp
@@ -5337,7 +5337,7 @@ public:
   virtual nsresult BindToTree(nsIDocument* aDocument, nsIContent* aParent,
                               nsIContent* aBindingParent,
                               PRBool aCompileEventHandlers);
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   // imgIDecoderObserver
   NS_IMETHOD OnStopDecode(imgIRequest *aRequest, nsresult status,
@@ -5488,7 +5488,7 @@ nsSVGFEImageElement::BindToTree(nsIDocument* aDocument, nsIContent* aParent,
   return rv;
 }
 
-PRInt32
+nsEventStates
 nsSVGFEImageElement::IntrinsicState() const
 {
   return nsSVGFEImageElementBase::IntrinsicState() |
diff --git a/content/svg/content/src/nsSVGImageElement.cpp b/content/svg/content/src/nsSVGImageElement.cpp
index 044ba8ee17e4..1386cdc74f4a 100644
--- a/content/svg/content/src/nsSVGImageElement.cpp
+++ b/content/svg/content/src/nsSVGImageElement.cpp
@@ -212,7 +212,7 @@ nsSVGImageElement::BindToTree(nsIDocument* aDocument, nsIContent* aParent,
   return rv;
 }
 
-PRInt32
+nsEventStates
 nsSVGImageElement::IntrinsicState() const
 {
   return nsSVGImageElementBase::IntrinsicState() |
diff --git a/content/svg/content/src/nsSVGImageElement.h b/content/svg/content/src/nsSVGImageElement.h
index 55d40aa8adda..3cc5e79a2323 100644
--- a/content/svg/content/src/nsSVGImageElement.h
+++ b/content/svg/content/src/nsSVGImageElement.h
@@ -81,7 +81,7 @@ public:
                               nsIContent* aBindingParent,
                               PRBool aCompileEventHandlers);
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   NS_IMETHOD_(PRBool) IsAttributeMapped(const nsIAtom* name) const;
 
diff --git a/content/xtf/src/nsXTFElementWrapper.cpp b/content/xtf/src/nsXTFElementWrapper.cpp
index 2a34b14851e7..b9e93c5c9ed4 100644
--- a/content/xtf/src/nsXTFElementWrapper.cpp
+++ b/content/xtf/src/nsXTFElementWrapper.cpp
@@ -543,13 +543,13 @@ nsXTFElementWrapper::GetExistingAttrNameFromQName(const nsAString& aStr) const
   return nodeInfo;
 }
 
-PRInt32
+nsEventStates
 nsXTFElementWrapper::IntrinsicState() const
 {
-  PRInt32 retState = nsXTFElementWrapperBase::IntrinsicState();
-  if (mIntrinsicState & NS_EVENT_STATE_MOZ_READONLY) {
+  nsEventStates retState = nsXTFElementWrapperBase::IntrinsicState();
+  if (mIntrinsicState.HasState(NS_EVENT_STATE_MOZ_READONLY)) {
     retState &= ~NS_EVENT_STATE_MOZ_READWRITE;
-  } else if (mIntrinsicState & NS_EVENT_STATE_MOZ_READWRITE) {
+  } else if (mIntrinsicState.HasState(NS_EVENT_STATE_MOZ_READWRITE)) {
     retState &= ~NS_EVENT_STATE_MOZ_READONLY;
   }
 
@@ -901,21 +901,22 @@ nsXTFElementWrapper::PostHandleEvent(nsEventChainPostVisitor& aVisitor)
 }
 
 NS_IMETHODIMP
-nsXTFElementWrapper::SetIntrinsicState(PRUint64 aNewState)
+nsXTFElementWrapper::SetIntrinsicState(nsEventStates::InternalType aNewState)
 {
   nsIDocument *doc = GetCurrentDoc();
-  PRUint64 bits = mIntrinsicState ^ aNewState;
-  
-  if (!doc || !bits)
+  nsEventStates newStates(aNewState);
+  nsEventStates bits = mIntrinsicState ^ newStates;
+
+  if (!doc || bits.IsEmpty())
     return NS_OK;
 
-  NS_WARN_IF_FALSE(!((aNewState & NS_EVENT_STATE_MOZ_READONLY) &&
-                   (aNewState & NS_EVENT_STATE_MOZ_READWRITE)),
+  NS_WARN_IF_FALSE(!newStates.HasAllStates(NS_EVENT_STATE_MOZ_READONLY |
+                                           NS_EVENT_STATE_MOZ_READWRITE),
                    "Both READONLY and READWRITE are being set.  Yikes!!!");
 
-  mIntrinsicState = aNewState;
+  mIntrinsicState = newStates;
   mozAutoDocUpdate upd(doc, UPDATE_CONTENT_STATE, PR_TRUE);
-  doc->ContentStatesChanged(this, nsnull, (PRInt32)bits);
+  doc->ContentStatesChanged(this, nsnull, bits);
 
   return NS_OK;
 }
diff --git a/content/xtf/src/nsXTFElementWrapper.h b/content/xtf/src/nsXTFElementWrapper.h
index e46188986efd..a24535f4caf1 100644
--- a/content/xtf/src/nsXTFElementWrapper.h
+++ b/content/xtf/src/nsXTFElementWrapper.h
@@ -108,7 +108,7 @@ public:
   PRUint32 GetAttrCount() const;
   virtual already_AddRefed<nsINodeInfo> GetExistingAttrNameFromQName(const nsAString& aStr) const;
 
-  virtual PRInt32 IntrinsicState() const;
+  virtual nsEventStates IntrinsicState() const;
 
   virtual void BeginAddingChildren();
   virtual nsresult DoneAddingChildren(PRBool aHaveNotified);
@@ -187,7 +187,7 @@ protected:
    * The intrinsic state of the element.
    * @see nsIContent::IntrinsicState()
    */
-  PRUint64 mIntrinsicState;
+  nsEventStates mIntrinsicState;
 
   // Temporary owner used by GetAttrNameAt
   nsAttrName mTmpAttrName;
diff --git a/content/xul/content/src/nsXULElement.cpp b/content/xul/content/src/nsXULElement.cpp
index ab6e567d6d53..7473b31ca8ce 100644
--- a/content/xul/content/src/nsXULElement.cpp
+++ b/content/xul/content/src/nsXULElement.cpp
@@ -1355,9 +1355,9 @@ nsXULElement::UnsetAttr(PRInt32 aNameSpaceID, nsIAtom* aName, PRBool aNotify)
 
     // When notifying, make sure to keep track of states whose value
     // depends solely on the value of an attribute.
-    PRUint32 stateMask;
+    nsEventStates stateMask;
     if (aNotify) {
-        stateMask = PRUint32(IntrinsicState());
+        stateMask = IntrinsicState();
  
         nsNodeUtils::AttributeWillChange(this, aNameSpaceID, aName,
                                          nsIDOMMutationEvent::REMOVAL);
@@ -1459,8 +1459,8 @@ nsXULElement::UnsetAttr(PRInt32 aNameSpaceID, nsIAtom* aName, PRBool aNotify)
     }
 
     if (aNotify) {
-        stateMask = stateMask ^ PRUint32(IntrinsicState());
-        if (stateMask && doc) {
+        stateMask ^= IntrinsicState();
+        if (doc && !stateMask.IsEmpty()) {
             MOZ_AUTO_DOC_UPDATE(doc, UPDATE_CONTENT_STATE, aNotify);
             doc->ContentStatesChanged(this, nsnull, stateMask);
         }
@@ -2239,10 +2239,10 @@ nsXULElement::AddPopupListener(nsIAtom* aName)
     return NS_OK;
 }
 
-PRInt32
+nsEventStates
 nsXULElement::IntrinsicState() const
 {
-    PRInt32 state = nsStyledElement::IntrinsicState();
+    nsEventStates state = nsStyledElement::IntrinsicState();
 
     const nsIAtom* tag = Tag();
     if (GetNameSpaceID() == kNameSpaceID_XUL &&
diff --git a/content/xul/content/src/nsXULElement.h b/content/xul/content/src/nsXULElement.h
index b189c1c2bf60..6ae72a69d3a3 100644
--- a/content/xul/content/src/nsXULElement.h
+++ b/content/xul/content/src/nsXULElement.h
@@ -564,7 +564,7 @@ public:
     NS_DECL_NSIDOMXULELEMENT
 
     virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
-    virtual PRInt32 IntrinsicState() const;
+    virtual nsEventStates IntrinsicState() const;
 
     nsresult EnsureLocalStyle();
 
diff --git a/editor/libeditor/html/nsHTMLEditor.cpp b/editor/libeditor/html/nsHTMLEditor.cpp
index 12348c7764a8..99df6b0f12b9 100644
--- a/editor/libeditor/html/nsHTMLEditor.cpp
+++ b/editor/libeditor/html/nsHTMLEditor.cpp
@@ -3909,7 +3909,7 @@ nsHTMLEditor::IsModifiableNode(nsIDOMNode *aNode)
 {
   nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
 
-  return !content || !(content->IntrinsicState() & NS_EVENT_STATE_MOZ_READONLY);
+  return !content || !content->IntrinsicState().HasState(NS_EVENT_STATE_MOZ_READONLY);
 }
 
 static nsresult SetSelectionAroundHeadChildren(nsCOMPtr<nsISelection> aSelection, nsWeakPtr aDocWeak)
diff --git a/extensions/spellcheck/src/mozInlineSpellChecker.cpp b/extensions/spellcheck/src/mozInlineSpellChecker.cpp
index e808310623f0..c401051c7a69 100644
--- a/extensions/spellcheck/src/mozInlineSpellChecker.cpp
+++ b/extensions/spellcheck/src/mozInlineSpellChecker.cpp
@@ -1160,7 +1160,7 @@ mozInlineSpellChecker::SkipSpellCheckForNode(nsIEditor* aEditor,
   else {
     // XXX Do we really want this for all read-write content?
     nsCOMPtr<nsIContent> content = do_QueryInterface(aNode);
-    *checkSpelling = !!(content->IntrinsicState() & NS_EVENT_STATE_MOZ_READWRITE);
+    *checkSpelling = content->IntrinsicState().HasState(NS_EVENT_STATE_MOZ_READWRITE);
   }
 
   return NS_OK;
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 6b4887747105..2043edd329d7 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -1883,7 +1883,7 @@ nsCSSFrameConstructor::ConstructTable(nsFrameConstructorState& aState,
   nsIContent* const content = aItem.mContent;
   nsStyleContext* const styleContext = aItem.mStyleContext;
   const PRUint32 nameSpaceID = aItem.mNameSpaceID;
-  
+
   nsresult rv = NS_OK;
 
   // create the pseudo SC for the outer table as a child of the inner SC
@@ -3650,9 +3650,9 @@ nsCSSFrameConstructor::FindObjectData(nsIContent* aContent,
   // cases when the object is broken/suppressed/etc (e.g. a broken image), but
   // we want to treat those cases as TYPE_NULL
   PRUint32 type;
-  if (aContent->IntrinsicState() &
-      (NS_EVENT_STATE_BROKEN | NS_EVENT_STATE_USERDISABLED |
-       NS_EVENT_STATE_SUPPRESSED)) {
+  if (aContent->IntrinsicState().HasAtLeastOneOfStates(NS_EVENT_STATE_BROKEN |
+                                                       NS_EVENT_STATE_USERDISABLED |
+                                                       NS_EVENT_STATE_SUPPRESSED)) {
     type = nsIObjectLoadingContent::TYPE_NULL;
   } else {
     nsCOMPtr<nsIObjectLoadingContent> objContent(do_QueryInterface(aContent));
@@ -8035,7 +8035,7 @@ nsCSSFrameConstructor::RestyleElement(Element        *aElement,
 nsresult
 nsCSSFrameConstructor::ContentStatesChanged(nsIContent* aContent1,
                                             nsIContent* aContent2,
-                                            PRInt32 aStateMask) 
+                                            nsEventStates aStateMask)
 {
   // XXXbz it would be good if this function only took Elements, but
   // we'd have to make ESM guarantee that usefully.
@@ -8050,7 +8050,7 @@ nsCSSFrameConstructor::ContentStatesChanged(nsIContent* aContent1,
 
 void
 nsCSSFrameConstructor::DoContentStateChanged(Element* aElement,
-                                             PRInt32 aStateMask) 
+                                             nsEventStates aStateMask)
 {
   nsStyleSet *styleSet = mPresShell->StyleSet();
   nsPresContext *presContext = mPresShell->GetPresContext();
@@ -8067,8 +8067,10 @@ nsCSSFrameConstructor::DoContentStateChanged(Element* aElement,
   if (primaryFrame) {
     // If it's generated content, ignore LOADING/etc state changes on it.
     if (!primaryFrame->IsGeneratedContentFrame() &&
-        (aStateMask & (NS_EVENT_STATE_BROKEN | NS_EVENT_STATE_USERDISABLED |
-                       NS_EVENT_STATE_SUPPRESSED | NS_EVENT_STATE_LOADING))) {
+        aStateMask.HasAtLeastOneOfStates(NS_EVENT_STATE_BROKEN |
+                                  NS_EVENT_STATE_USERDISABLED |
+                                  NS_EVENT_STATE_SUPPRESSED |
+                                  NS_EVENT_STATE_LOADING)) {
       hint = nsChangeHint_ReconstructFrame;
     } else {
       PRUint8 app = primaryFrame->GetStyleDisplay()->mAppearance;
@@ -8089,11 +8091,11 @@ nsCSSFrameConstructor::DoContentStateChanged(Element* aElement,
   nsRestyleHint rshint = 
     styleSet->HasStateDependentStyle(presContext, aElement, aStateMask);
       
-  if ((aStateMask & NS_EVENT_STATE_HOVER) && rshint != 0) {
+  if (aStateMask.HasState(NS_EVENT_STATE_HOVER) && rshint != 0) {
     ++mHoverGeneration;
   }
 
-  if (aStateMask & NS_EVENT_STATE_VISITED) {
+  if (aStateMask.HasState(NS_EVENT_STATE_VISITED)) {
     // Exposing information to the page about whether the link is
     // visited or not isn't really something we can worry about here.
     // FIXME: We could probably do this a bit better.
diff --git a/layout/base/nsCSSFrameConstructor.h b/layout/base/nsCSSFrameConstructor.h
index a680028d99b6..753f7746b3fa 100644
--- a/layout/base/nsCSSFrameConstructor.h
+++ b/layout/base/nsCSSFrameConstructor.h
@@ -235,9 +235,9 @@ public:
   nsresult CharacterDataChanged(nsIContent* aContent,
                                 CharacterDataChangeInfo* aInfo);
 
-  nsresult ContentStatesChanged(nsIContent*     aContent1,
-                                nsIContent*     aContent2,
-                                PRInt32         aStateMask);
+  nsresult ContentStatesChanged(nsIContent*   aContent1,
+                                nsIContent*   aContent2,
+                                nsEventStates aStateMask);
 
   // generate the child frames and process bindings
   nsresult GenerateChildFrames(nsIFrame* aFrame);
@@ -416,7 +416,7 @@ private:
                               nsIFrame*&     aCanvasFrame);
 
   void DoContentStateChanged(Element* aElement,
-                             PRInt32 aStateMask);
+                             nsEventStates aStateMask);
 
   /* aMinHint is the minimal change that should be made to the element */
   // XXXbz do we really need the aPrimaryFrame argument here?
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 9ea039a1b8d6..47b62ff7aad3 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -4953,7 +4953,7 @@ void
 PresShell::ContentStatesChanged(nsIDocument* aDocument,
                                 nsIContent* aContent1,
                                 nsIContent* aContent2,
-                                PRInt32 aStateMask)
+                                nsEventStates aStateMask)
 {
   NS_PRECONDITION(!mIsDocumentGone, "Unexpected ContentStatesChanged");
   NS_PRECONDITION(aDocument == mDocument, "Unexpected aDocument");
@@ -4967,7 +4967,7 @@ PresShell::ContentStatesChanged(nsIDocument* aDocument,
 
 void
 PresShell::DocumentStatesChanged(nsIDocument* aDocument,
-                                 PRInt32 aStateMask)
+                                 nsEventStates aStateMask)
 {
   NS_PRECONDITION(!mIsDocumentGone, "Unexpected DocumentStatesChanged");
   NS_PRECONDITION(aDocument == mDocument, "Unexpected aDocument");
@@ -4981,7 +4981,7 @@ PresShell::DocumentStatesChanged(nsIDocument* aDocument,
     VERIFY_STYLE_TREE;
   }
 
-  if (aStateMask & NS_DOCUMENT_STATE_WINDOW_INACTIVE) {
+  if (aStateMask.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
     nsIFrame* root = FrameManager()->GetRootFrame();
     if (root) {
       // It's a display root. So, invalidate the layer contents of
diff --git a/layout/forms/nsButtonFrameRenderer.cpp b/layout/forms/nsButtonFrameRenderer.cpp
index a870e9c2f085..e4bc9ad38a9e 100644
--- a/layout/forms/nsButtonFrameRenderer.cpp
+++ b/layout/forms/nsButtonFrameRenderer.cpp
@@ -89,7 +89,7 @@ nsButtonFrameRenderer::isDisabled()
 {
   // NOTE: we might want to remove this method to prevent calling too often
   // IntrinsicState().
-  return (mFrame->GetContent()->IntrinsicState() & NS_EVENT_STATE_DISABLED) != 0;
+  return mFrame->GetContent()->IntrinsicState().HasState(NS_EVENT_STATE_DISABLED);
 }
 
 class nsDisplayButtonBoxShadowOuter : public nsDisplayItem {
diff --git a/layout/forms/nsComboboxControlFrame.cpp b/layout/forms/nsComboboxControlFrame.cpp
index b627680a12ab..866afb26d0d7 100644
--- a/layout/forms/nsComboboxControlFrame.cpp
+++ b/layout/forms/nsComboboxControlFrame.cpp
@@ -728,8 +728,8 @@ nsComboboxControlFrame::GetFrameName(nsAString& aResult) const
 void
 nsComboboxControlFrame::ShowDropDown(PRBool aDoDropDown) 
 {
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED) {
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED)) {
     return;
   }
 
@@ -928,8 +928,8 @@ nsComboboxControlFrame::HandleEvent(nsPresContext* aPresContext,
     return NS_OK;
   }
 
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED) {
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED)) {
     return NS_OK;
   }
 
@@ -1386,8 +1386,8 @@ void nsComboboxControlFrame::PaintFocus(nsIRenderingContext& aRenderingContext,
                                         nsPoint aPt)
 {
   /* Do we need to do anything? */
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if ((eventStates & NS_EVENT_STATE_DISABLED) || mFocused != this)
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED) || mFocused != this)
     return;
 
   aRenderingContext.PushState();
diff --git a/layout/forms/nsFileControlFrame.cpp b/layout/forms/nsFileControlFrame.cpp
index 97a32435c763..8e960b0d4b3a 100644
--- a/layout/forms/nsFileControlFrame.cpp
+++ b/layout/forms/nsFileControlFrame.cpp
@@ -681,8 +681,8 @@ nsFileControlFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
   // Disabled file controls don't pass mouse events to their children, so we
   // put an invisible item in the display list above the children
   // just to catch events
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if ((eventStates & NS_EVENT_STATE_DISABLED) && IsVisibleForPainting(aBuilder)) {
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED) && IsVisibleForPainting(aBuilder)) {
     rv = aLists.Content()->AppendNewToTop(
         new (aBuilder) nsDisplayEventReceiver(aBuilder, this));
     if (NS_FAILED(rv))
diff --git a/layout/forms/nsListControlFrame.cpp b/layout/forms/nsListControlFrame.cpp
index eb244f9a3974..8a4fb893cdcb 100644
--- a/layout/forms/nsListControlFrame.cpp
+++ b/layout/forms/nsListControlFrame.cpp
@@ -1101,8 +1101,8 @@ nsListControlFrame::HandleEvent(nsPresContext* aPresContext,
   if (uiStyle->mUserInput == NS_STYLE_USER_INPUT_NONE || uiStyle->mUserInput == NS_STYLE_USER_INPUT_DISABLED)
     return nsFrame::HandleEvent(aPresContext, aEvent, aEventStatus);
 
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED)
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED))
     return NS_OK;
 
   return nsHTMLScrollFrame::HandleEvent(aPresContext, aEvent, aEventStatus);
@@ -1962,8 +1962,8 @@ nsListControlFrame::MouseUp(nsIDOMEvent* aMouseEvent)
 
   mButtonDown = PR_FALSE;
 
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED) {
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED)) {
     return NS_OK;
   }
 
@@ -2172,8 +2172,8 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
 
   UpdateInListState(aMouseEvent);
 
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED) {
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED)) {
     return NS_OK;
   }
 
@@ -2479,8 +2479,8 @@ nsListControlFrame::KeyPress(nsIDOMEvent* aKeyEvent)
 {
   NS_ASSERTION(aKeyEvent, "keyEvent is null.");
 
-  PRInt32 eventStates = mContent->IntrinsicState();
-  if (eventStates & NS_EVENT_STATE_DISABLED)
+  nsEventStates eventStates = mContent->IntrinsicState();
+  if (eventStates.HasState(NS_EVENT_STATE_DISABLED))
     return NS_OK;
 
   // Start by making sure we can query for a key event
diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index 90fdf5900855..0904b7d5872e 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -448,17 +448,17 @@ nsImageFrame::SourceRectToDest(const nsIntRect& aRect)
 
 // This is a macro so that we don't evaluate the boolean last arg
 // unless we have to; it can be expensive
-#define IMAGE_OK(_state, _loadingOK)                        \
-   (((_state) & BAD_STATES) == 0 ||                         \
-    (((_state) & BAD_STATES) == NS_EVENT_STATE_LOADING &&   \
-     (_loadingOK)))
+#define IMAGE_OK(_state, _loadingOK)                                           \
+   (!(_state).HasAtLeastOneOfStates(BAD_STATES) ||                                    \
+    (!(_state).HasAtLeastOneOfStates(NS_EVENT_STATE_BROKEN | NS_EVENT_STATE_USERDISABLED) && \
+     (_state).HasState(NS_EVENT_STATE_LOADING) && (_loadingOK)))
 
 /* static */
 PRBool
 nsImageFrame::ShouldCreateImageFrameFor(nsIContent* aContent,
                                         nsStyleContext* aStyleContext)
 {
-  PRInt32 state = aContent->IntrinsicState();
+  nsEventStates state = aContent->IntrinsicState();
   if (IMAGE_OK(state,
                HaveFixedSize(aStyleContext->GetStylePosition()))) {
     // Image is fine; do the image frame thing
@@ -1261,7 +1261,7 @@ nsImageFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                               getter_AddRefs(currentRequest));
     }
 
-    PRInt32 contentState = mContent->IntrinsicState();
+    nsEventStates contentState = mContent->IntrinsicState();
     PRBool imageOK = IMAGE_OK(contentState, PR_TRUE);
 
     nsCOMPtr<imgIContainer> imgCon;
diff --git a/layout/inspector/src/inDOMUtils.cpp b/layout/inspector/src/inDOMUtils.cpp
index d3f2994fbea7..0adec0bd072e 100644
--- a/layout/inspector/src/inDOMUtils.cpp
+++ b/layout/inspector/src/inDOMUtils.cpp
@@ -232,7 +232,7 @@ inDOMUtils::GetBindingURLs(nsIDOMElement *aElement, nsIArray **_retval)
 }
 
 NS_IMETHODIMP
-inDOMUtils::SetContentState(nsIDOMElement *aElement, PRUint64 aState)
+inDOMUtils::SetContentState(nsIDOMElement *aElement, nsEventStates::InternalType aState)
 {
   NS_ENSURE_ARG_POINTER(aElement);
   
@@ -241,14 +241,14 @@ inDOMUtils::SetContentState(nsIDOMElement *aElement, PRUint64 aState)
     nsCOMPtr<nsIContent> content;
     content = do_QueryInterface(aElement);
   
-    return esm->SetContentState(content, (PRInt32)aState);
+    return esm->SetContentState(content, nsEventStates(aState));
   }
   
   return NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
-inDOMUtils::GetContentState(nsIDOMElement *aElement, PRUint64* aState)
+inDOMUtils::GetContentState(nsIDOMElement *aElement, nsEventStates::InternalType* aState)
 {
   *aState = 0;
 
@@ -258,7 +258,9 @@ inDOMUtils::GetContentState(nsIDOMElement *aElement, PRUint64* aState)
   if (esm) {
     nsCOMPtr<nsIContent> content;
     content = do_QueryInterface(aElement);
-    *aState = esm->GetContentState(content);
+    // NOTE: if this method is removed,
+    // please remove GetInternalValue from nsEventStates
+    *aState = esm->GetContentState(content).GetInternalValue();
     return NS_OK;
   }
 
diff --git a/layout/style/nsCSSRuleProcessor.cpp b/layout/style/nsCSSRuleProcessor.cpp
index 3ce148ff8388..99836a17c584 100644
--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -818,7 +818,7 @@ struct RuleCascadeData {
   RuleHash*
     mPseudoElementRuleHashes[nsCSSPseudoElements::ePseudo_PseudoElementCount];
   nsTArray<nsCSSSelector*> mStateSelectors;
-  PRUint32                 mSelectorDocumentStates;
+  nsEventStates            mSelectorDocumentStates;
   PLDHashTable             mClassSelectors;
   nsTArray<nsCSSSelector*> mPossiblyNegatedClassSelectors;
   nsTArray<nsCSSSelector*> mIDSelectors;
@@ -1228,7 +1228,7 @@ const nsString* RuleProcessorData::GetLang()
   return mLanguage;
 }
 
-PRUint32
+nsEventStates
 RuleProcessorData::ContentState()
 {
   if (!mGotContentState) {
@@ -1243,15 +1243,15 @@ RuleProcessorData::ContentState()
     // expose that :visited support is disabled to the Web page.
     if ((!gSupportVisitedPseudo ||
         gPrivateBrowsingObserver->InPrivateBrowsing()) &&
-        (mContentState & NS_EVENT_STATE_VISITED)) {
-      mContentState = (mContentState & ~PRUint32(NS_EVENT_STATE_VISITED)) |
-                      NS_EVENT_STATE_UNVISITED;
+        mContentState.HasState(NS_EVENT_STATE_VISITED)) {
+      mContentState &= ~NS_EVENT_STATE_VISITED;
+      mContentState |= NS_EVENT_STATE_UNVISITED;
     }
   }
   return mContentState;
 }
 
-PRUint32
+nsEventStates
 RuleProcessorData::DocumentState()
 {
   return mElement->GetOwnerDoc()->GetDocumentState();
@@ -1260,20 +1260,19 @@ RuleProcessorData::DocumentState()
 PRBool
 RuleProcessorData::IsLink()
 {
-  PRUint32 state = ContentState();
-  return (state & (NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED)) != 0;
+  nsEventStates state = ContentState();
+  return state.HasAtLeastOneOfStates(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED);
 }
 
-PRUint32
+nsEventStates
 RuleProcessorData::GetContentStateForVisitedHandling(
                      nsRuleWalker::VisitedHandlingType aVisitedHandling,
                      PRBool aIsRelevantLink)
 {
-  PRUint32 contentState = ContentState();
-  if (contentState & (NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED)) {
+  nsEventStates contentState = ContentState();
+  if (contentState.HasAtLeastOneOfStates(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED)) {
     NS_ABORT_IF_FALSE(IsLink(), "IsLink() should match state");
-    contentState &=
-      ~PRUint32(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED);
+    contentState &= ~(NS_EVENT_STATE_VISITED | NS_EVENT_STATE_UNVISITED);
     if (aIsRelevantLink) {
       switch (aVisitedHandling) {
         case nsRuleWalker::eRelevantLinkUnvisited:
@@ -1415,7 +1414,7 @@ struct NodeMatchContext {
   // we do separate notifications then we might determine the style is
   // not state-dependent when it really is (e.g., determining that a
   // :hover:active rule no longer matches when both states are unset).
-  const PRInt32 mStateMask;
+  const nsEventStates mStateMask;
 
   // Is this link the unique link whose visitedness can affect the style
   // of the node being matched?  (That link is the nearest link to the
@@ -1428,7 +1427,7 @@ struct NodeMatchContext {
   // mForStyling is false, we have to assume we don't know.)
   const PRBool mIsRelevantLink;
 
-  NodeMatchContext(PRInt32 aStateMask, PRBool aIsRelevantLink)
+  NodeMatchContext(nsEventStates aStateMask, PRBool aIsRelevantLink)
     : mStateMask(aStateMask)
     , mIsRelevantLink(aIsRelevantLink)
   {
@@ -1630,21 +1629,21 @@ checkGenericEmptyMatches(RuleProcessorData& data,
   return (child == nsnull);
 }
 
-// An array of the bits that are relevant for various pseudoclasses.
-static const PRUint32 sPseudoClassBits[] = {
+// An array of the states that are relevant for various pseudoclasses.
+static const nsEventStates sPseudoClassStates[] = {
 #define CSS_PSEUDO_CLASS(_name, _value)         \
-  0,
-#define CSS_STATE_PSEUDO_CLASS(_name, _value, _bit) \
-  _bit,
+  nsEventStates(),
+#define CSS_STATE_PSEUDO_CLASS(_name, _value, _states) \
+  _states,
 #include "nsCSSPseudoClassList.h"
 #undef CSS_STATE_PSEUDO_CLASS
 #undef CSS_PSEUDO_CLASS
   // Add more entries for our fake values to make sure we can't
   // index out of bounds into this array no matter what.
-  0,
-  0
+  nsEventStates(),
+  nsEventStates()
 };
-PR_STATIC_ASSERT(NS_ARRAY_LENGTH(sPseudoClassBits) ==
+PR_STATIC_ASSERT(NS_ARRAY_LENGTH(sPseudoClassStates) ==
                    nsCSSPseudoClasses::ePseudoClass_NotPseudoClass + 1);
 
 // |aDependence| has two functions:
@@ -1741,7 +1740,7 @@ static PRBool SelectorMatches(RuleProcessorData &data,
   // generally quick to test, and thus earlier).  If they were later,
   // we'd probably avoid setting those bits in more cases where setting
   // them is unnecessary.
-  NS_ASSERTION(aNodeMatchContext.mStateMask == 0 ||
+  NS_ASSERTION(aNodeMatchContext.mStateMask.IsEmpty() ||
                !aTreeMatchContext.mForStyling,
                "mForStyling must be false if we're just testing for "
                "state-dependence");
@@ -1749,8 +1748,8 @@ static PRBool SelectorMatches(RuleProcessorData &data,
   // test for pseudo class match
   for (nsPseudoClassList* pseudoClass = aSelector->mPseudoClassList;
        pseudoClass; pseudoClass = pseudoClass->mNext) {
-    PRInt32 statesToCheck = sPseudoClassBits[pseudoClass->mType];
-    if (!statesToCheck) {
+    nsEventStates statesToCheck = sPseudoClassStates[pseudoClass->mType];
+    if (statesToCheck.IsEmpty()) {
       // keep the cases here in the same order as the list in
       // nsCSSPseudoClassList.h
       switch (pseudoClass->mType) {
@@ -2026,7 +2025,7 @@ static PRBool SelectorMatches(RuleProcessorData &data,
       case nsCSSPseudoClasses::ePseudoClass_mozLocaleDir:
         {
           PRBool docIsRTL =
-            (data.DocumentState() & NS_DOCUMENT_STATE_RTL_LOCALE) != 0;
+            data.DocumentState().HasState(NS_DOCUMENT_STATE_RTL_LOCALE);
 
           nsDependentString dirString(pseudoClass->u.mString);
           NS_ASSERTION(dirString.EqualsLiteral("ltr") ||
@@ -2070,7 +2069,7 @@ static PRBool SelectorMatches(RuleProcessorData &data,
         break;
 
       case nsCSSPseudoClasses::ePseudoClass_mozWindowInactive:
-        if ((data.DocumentState() & NS_DOCUMENT_STATE_WINDOW_INACTIVE) == 0) {
+        if (!data.DocumentState().HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
           return PR_FALSE;
         }
         break;
@@ -2095,7 +2094,7 @@ static PRBool SelectorMatches(RuleProcessorData &data,
       }
     } else {
       // Bit-based pseudo-classes
-      if ((statesToCheck & (NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE)) &&
+      if (statesToCheck.HasAtLeastOneOfStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE) &&
           data.mCompatMode == eCompatibility_NavQuirks &&
           // global selector (but don't check .class):
           !aSelector->HasTagSelector() && !aSelector->mIDList && 
@@ -2112,14 +2111,14 @@ static PRBool SelectorMatches(RuleProcessorData &data,
         // selectors ":hover" and ":active".
         return PR_FALSE;
       } else {
-        if (aNodeMatchContext.mStateMask & statesToCheck) {
+        if (aNodeMatchContext.mStateMask.HasAtLeastOneOfStates(statesToCheck)) {
           if (aDependence)
             *aDependence = PR_TRUE;
         } else {
-          PRUint32 contentState = data.GetContentStateForVisitedHandling(
-                                    aTreeMatchContext.mVisitedHandling,
-                                    aNodeMatchContext.mIsRelevantLink);
-          if (!(contentState & statesToCheck)) {
+          nsEventStates contentState = data.GetContentStateForVisitedHandling(
+                                         aTreeMatchContext.mVisitedHandling,
+                                         aNodeMatchContext.mIsRelevantLink);
+          if (!contentState.HasAtLeastOneOfStates(statesToCheck)) {
             return PR_FALSE;
           }
         }
@@ -2296,7 +2295,8 @@ static PRBool SelectorMatchesTree(RuleProcessorData& aPrevData,
     if (! data) {
       return PR_FALSE;
     }
-    NodeMatchContext nodeContext(0, aLookForRelevantLink && data->IsLink());
+    NodeMatchContext nodeContext(nsEventStates(), aLookForRelevantLink &&
+                                                  data->IsLink());
     if (nodeContext.mIsRelevantLink) {
       // If we find an ancestor of the matched node that is a link
       // during the matching process, then it's the relevant link (see
@@ -2353,7 +2353,7 @@ static void ContentEnumFunc(nsICSSStyleRule* aRule, nsCSSSelector* aSelector,
   RuleProcessorData* data = (RuleProcessorData*)aData;
 
   TreeMatchContext treeContext(PR_TRUE, data->mRuleWalker->VisitedHandling());
-  NodeMatchContext nodeContext(0, data->IsLink());
+  NodeMatchContext nodeContext(nsEventStates(), data->IsLink());
   if (nodeContext.mIsRelevantLink) {
     treeContext.mHaveRelevantLink = PR_TRUE;
   }
@@ -2522,7 +2522,7 @@ nsCSSRuleProcessor::HasDocumentStateDependentStyle(StateRuleProcessorData* aData
 {
   RuleCascadeData* cascade = GetRuleCascade(aData->mPresContext);
 
-  return cascade && (cascade->mSelectorDocumentStates & aData->mStateMask) != 0;
+  return cascade && cascade->mSelectorDocumentStates.HasAtLeastOneOfStates(aData->mStateMask);
 }
 
 struct AttributeEnumData {
@@ -2546,7 +2546,7 @@ AttributeEnumFunc(nsCSSSelector* aSelector, AttributeEnumData* aData)
   // enumData->change won't change.
   TreeMatchContext treeContext(PR_FALSE,
                                nsRuleWalker::eLinksVisitedOrUnvisited);
-  NodeMatchContext nodeContext(0, PR_FALSE);
+  NodeMatchContext nodeContext(nsEventStates(), PR_FALSE);
   if ((possibleChange & ~(aData->change)) &&
       SelectorMatches(*data, aSelector, nodeContext, treeContext) &&
       SelectorMatchesTree(*data, aSelector->mNext, treeContext, PR_FALSE)) {
@@ -2698,7 +2698,7 @@ PRBool IsStateSelector(nsCSSSelector& aSelector)
     if (pseudoClass->mType >= nsCSSPseudoClasses::ePseudoClass_Count) {
       continue;
     }
-    if (sPseudoClassBits[pseudoClass->mType]) {
+    if (!sPseudoClassStates[pseudoClass->mType].IsEmpty()) {
       return PR_TRUE;
     }
   }
@@ -3160,7 +3160,7 @@ nsCSSRuleProcessor::SelectorListMatches(RuleProcessorData& aData,
     NS_ASSERTION(!sel->IsPseudoElement(), "Shouldn't have been called");
     TreeMatchContext treeContext(PR_FALSE,
                                  nsRuleWalker::eRelevantLinkUnvisited);
-    NodeMatchContext nodeContext(0, PR_FALSE);
+    NodeMatchContext nodeContext(nsEventStates(), PR_FALSE);
     if (SelectorMatches(aData, sel, nodeContext, treeContext)) {
       nsCSSSelector* next = sel->mNext;
       if (!next || SelectorMatchesTree(aData, next, treeContext, PR_FALSE)) {
diff --git a/layout/style/nsHTMLStyleSheet.cpp b/layout/style/nsHTMLStyleSheet.cpp
index 697de4fe9502..5528ae8e968f 100644
--- a/layout/style/nsHTMLStyleSheet.cpp
+++ b/layout/style/nsHTMLStyleSheet.cpp
@@ -220,23 +220,23 @@ nsHTMLStyleSheet::RulesMatching(ElementRuleProcessorData* aData)
     // if we have anchor colors, check if this is an anchor with an href
     if (tag == nsGkAtoms::a) {
       if (mLinkRule || mVisitedRule || mActiveRule) {
-        PRUint32 state = aData->GetContentStateForVisitedHandling(
+        nsEventStates state = aData->GetContentStateForVisitedHandling(
                                   ruleWalker->VisitedHandling(),
                                   // If the node being matched is a link,
                                   // it's the relevant link.
                                   aData->IsLink());
-        if (mLinkRule && (state & NS_EVENT_STATE_UNVISITED)) {
+        if (mLinkRule && state.HasState(NS_EVENT_STATE_UNVISITED)) {
           ruleWalker->Forward(mLinkRule);
           ruleWalker->SetHaveRelevantLink();
         }
-        else if (mVisitedRule && (state & NS_EVENT_STATE_VISITED)) {
+        else if (mVisitedRule && state.HasState(NS_EVENT_STATE_VISITED)) {
           ruleWalker->Forward(mVisitedRule);
           ruleWalker->SetHaveRelevantLink();
         }
 
         // No need to add to the active rule if it's not a link
         if (mActiveRule && aData->IsLink() &&
-            (state & NS_EVENT_STATE_ACTIVE)) {
+            state.HasState(NS_EVENT_STATE_ACTIVE)) {
           ruleWalker->Forward(mActiveRule);
         }
       } // end link/visited/active rules
@@ -275,9 +275,9 @@ nsHTMLStyleSheet::HasStateDependentStyle(StateRuleProcessorData* aData)
   if (aData->mIsHTMLContent &&
       aData->mContentTag == nsGkAtoms::a &&
       aData->IsLink() &&
-      ((mActiveRule && (aData->mStateMask & NS_EVENT_STATE_ACTIVE)) ||
-       (mLinkRule && (aData->mStateMask & NS_EVENT_STATE_VISITED)) ||
-       (mVisitedRule && (aData->mStateMask & NS_EVENT_STATE_VISITED)))) {
+      ((mActiveRule && aData->mStateMask.HasState(NS_EVENT_STATE_ACTIVE)) ||
+       (mLinkRule && aData->mStateMask.HasState(NS_EVENT_STATE_VISITED)) ||
+       (mVisitedRule && aData->mStateMask.HasState(NS_EVENT_STATE_VISITED)))) {
     return eRestyle_Self;
   }
   
diff --git a/layout/style/nsRuleProcessorData.h b/layout/style/nsRuleProcessorData.h
index 1c78c63107eb..223c964ab800 100644
--- a/layout/style/nsRuleProcessorData.h
+++ b/layout/style/nsRuleProcessorData.h
@@ -106,13 +106,13 @@ private:
   }
 public:
   const nsString* GetLang();
-  PRUint32 ContentState();
-  PRUint32 DocumentState();
+  nsEventStates ContentState();
+  nsEventStates DocumentState();
   PRBool IsLink();
 
-  PRUint32 GetContentStateForVisitedHandling(
-             nsRuleWalker::VisitedHandlingType aVisitedHandling,
-             PRBool aIsRelevantLink);
+  nsEventStates GetContentStateForVisitedHandling(
+                  nsRuleWalker::VisitedHandlingType aVisitedHandling,
+                  PRBool aIsRelevantLink);
 
   // Returns a 1-based index of the child in its parent.  If the child
   // is not in its parent's child list (i.e., it is anonymous content),
@@ -155,10 +155,11 @@ private:
   PRInt32 mNthIndices[2][2];
 
   // mContentState is initialized lazily.
-  PRInt32 mContentState;  // eventStateMgr->GetContentState() or
-                          // mElement->IntrinsicState() if we have no ESM
-                          // adjusted for not supporting :visited (but with
-                          // visitedness information when we support it)
+  nsEventStates mContentState;  // eventStateMgr->GetContentState() or
+                                // mElement->IntrinsicState() if we have no ESM
+                                // adjusted for not supporting :visited (but
+                                // with visitedness information when we support
+                                // it).
   PRPackedBool mGotContentState;
 };
 
@@ -234,14 +235,14 @@ struct XULTreeRuleProcessorData : public RuleProcessorData {
 struct StateRuleProcessorData : public RuleProcessorData {
   StateRuleProcessorData(nsPresContext* aPresContext,
                          mozilla::dom::Element* aElement,
-                         PRInt32 aStateMask)
+                         nsEventStates aStateMask)
     : RuleProcessorData(aPresContext, aElement, nsnull),
       mStateMask(aStateMask)
   {
     NS_PRECONDITION(aPresContext, "null pointer");
   }
-  const PRInt32 mStateMask; // |HasStateDependentStyle| for which state(s)?
-                            //  Constants defined in nsIEventStateManager.h .
+  const nsEventStates mStateMask; // |HasStateDependentStyle| for which state(s)?
+                                  //  Constants defined in nsEventStates.h .
 };
 
 struct AttributeRuleProcessorData : public RuleProcessorData {
diff --git a/layout/style/nsStyleSet.cpp b/layout/style/nsStyleSet.cpp
index a32895717044..af04bee4d98b 100644
--- a/layout/style/nsStyleSet.cpp
+++ b/layout/style/nsStyleSet.cpp
@@ -805,7 +805,7 @@ nsStyleSet::ResolveStyleFor(Element* aElement,
 
   return GetContext(aParentContext, ruleNode, visitedRuleNode,
                     data.IsLink(),
-                    (data.ContentState() & NS_EVENT_STATE_VISITED) != 0,
+                    data.ContentState().HasState(NS_EVENT_STATE_VISITED),
                     nsnull, nsCSSPseudoElements::ePseudo_NotPseudoElement);
 }
 
@@ -1212,7 +1212,7 @@ nsStyleSet::ReparentStyleContext(nsStyleContext* aStyleContext,
 
 struct StatefulData : public StateRuleProcessorData {
   StatefulData(nsPresContext* aPresContext,
-               Element* aElement, PRInt32 aStateMask)
+               Element* aElement, nsEventStates aStateMask)
     : StateRuleProcessorData(aPresContext, aElement, aStateMask),
       mHint(nsRestyleHint(0))
   {}
@@ -1234,7 +1234,7 @@ static PRBool SheetHasDocumentStateStyle(nsIStyleRuleProcessor* aProcessor,
 PRBool
 nsStyleSet::HasDocumentStateDependentStyle(nsPresContext* aPresContext,
                                            nsIContent*    aContent,
-                                           PRInt32        aStateMask)
+                                           nsEventStates  aStateMask)
 {
   if (!aContent || !aContent->IsElement())
     return PR_FALSE;
@@ -1255,9 +1255,9 @@ static PRBool SheetHasStatefulStyle(nsIStyleRuleProcessor* aProcessor,
 
 // Test if style is dependent on content state
 nsRestyleHint
-nsStyleSet::HasStateDependentStyle(nsPresContext* aPresContext,
-                                   Element*       aElement,
-                                   PRInt32        aStateMask)
+nsStyleSet::HasStateDependentStyle(nsPresContext*       aPresContext,
+                                   Element*             aElement,
+                                   nsEventStates        aStateMask)
 {
   StatefulData data(aPresContext, aElement, aStateMask);
   WalkRuleProcessors(SheetHasStatefulStyle, &data, PR_FALSE);
diff --git a/layout/style/nsStyleSet.h b/layout/style/nsStyleSet.h
index 568dc156ca35..8d387ceb784a 100644
--- a/layout/style/nsStyleSet.h
+++ b/layout/style/nsStyleSet.h
@@ -185,12 +185,12 @@ class nsStyleSet
   // Test if style is dependent on a document state.
   PRBool HasDocumentStateDependentStyle(nsPresContext* aPresContext,
                                         nsIContent*    aContent,
-                                        PRInt32        aStateMask);
+                                        nsEventStates  aStateMask);
 
   // Test if style is dependent on content state
   nsRestyleHint HasStateDependentStyle(nsPresContext* aPresContext,
                                        mozilla::dom::Element* aElement,
-                                       PRInt32 aStateMask);
+                                       nsEventStates aStateMask);
 
   // Test if style is dependent on the presence of an attribute.
   nsRestyleHint HasAttributeDependentStyle(nsPresContext* aPresContext,
diff --git a/layout/xul/base/src/nsButtonBoxFrame.cpp b/layout/xul/base/src/nsButtonBoxFrame.cpp
index 139f57baeb74..9048edd910bf 100644
--- a/layout/xul/base/src/nsButtonBoxFrame.cpp
+++ b/layout/xul/base/src/nsButtonBoxFrame.cpp
@@ -121,10 +121,10 @@ nsButtonBoxFrame::HandleEvent(nsPresContext* aPresContext,
         nsKeyEvent* keyEvent = (nsKeyEvent*)aEvent;
         if (NS_VK_SPACE == keyEvent->keyCode) {
           // only activate on keyup if we're already in the :hover:active state
-          const PRInt32 activeHover = NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER;
+          const nsEventStates activeHover = NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER;
           nsIEventStateManager *esm = aPresContext->EventStateManager();
-          PRInt32 buttonState = esm->GetContentState(mContent);
-          if ((buttonState & activeHover) == activeHover) {
+          nsEventStates buttonState = esm->GetContentState(mContent);
+          if (buttonState.HasAllStates(activeHover)) {
             esm->SetContentState(nsnull, activeHover);    // return to normal state
             MouseClicked(aPresContext, aEvent);
           }
diff --git a/layout/xul/base/src/nsMenuPopupFrame.cpp b/layout/xul/base/src/nsMenuPopupFrame.cpp
index 4504ab1440ee..9567f0f35f62 100644
--- a/layout/xul/base/src/nsMenuPopupFrame.cpp
+++ b/layout/xul/base/src/nsMenuPopupFrame.cpp
@@ -818,9 +818,9 @@ nsMenuPopupFrame::HidePopup(PRBool aDeselectMenu, nsPopupState aNewState)
   // This code may not the best solution, but we can leave it here until we find the better approach.
   nsIEventStateManager *esm = PresContext()->EventStateManager();
 
-  PRInt32 state = esm->GetContentState(mContent);
+  nsEventStates state = esm->GetContentState(mContent);
 
-  if (state & NS_EVENT_STATE_HOVER)
+  if (state.HasState(NS_EVENT_STATE_HOVER))
     esm->SetContentState(nsnull, NS_EVENT_STATE_HOVER);
 
   nsMenuFrame* menuFrame = GetParentMenu();
diff --git a/layout/xul/base/src/tree/src/nsTreeContentView.cpp b/layout/xul/base/src/tree/src/nsTreeContentView.cpp
index 68b3d9f00bf1..113260680c06 100644
--- a/layout/xul/base/src/tree/src/nsTreeContentView.cpp
+++ b/layout/xul/base/src/tree/src/nsTreeContentView.cpp
@@ -823,11 +823,11 @@ void
 nsTreeContentView::ContentStatesChanged(nsIDocument* aDocument,
                                         nsIContent* aContent1,
                                         nsIContent* aContent2,
-                                        PRInt32 aStateMask)
+                                        nsEventStates aStateMask)
 {
   if (!aContent1 || !mSelection ||
       !aContent1->IsHTML() ||
-      !(aStateMask & NS_EVENT_STATE_CHECKED))
+      !aStateMask.HasState(NS_EVENT_STATE_CHECKED))
     return;
 
   if (aContent1->Tag() == nsGkAtoms::option) {
diff --git a/parser/html/nsHtml5TreeOperation.cpp b/parser/html/nsHtml5TreeOperation.cpp
index 4345ca6acfa5..d85be89d3368 100644
--- a/parser/html/nsHtml5TreeOperation.cpp
+++ b/parser/html/nsHtml5TreeOperation.cpp
@@ -360,7 +360,7 @@ nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
 
           // the manual notification code is based on nsGenericElement
           
-          PRUint32 stateMask = PRUint32(node->IntrinsicState());
+          nsEventStates stateMask = node->IntrinsicState();
           nsNodeUtils::AttributeWillChange(node, 
                                            nsuri,
                                            localName,
@@ -382,8 +382,8 @@ nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
             }
           }
           
-          stateMask ^= PRUint32(node->IntrinsicState());
-          if (stateMask && document) {
+          stateMask ^= node->IntrinsicState();
+          if (!stateMask.IsEmpty() && document) {
             MOZ_AUTO_DOC_UPDATE(document, UPDATE_CONTENT_STATE, PR_TRUE);
             document->ContentStatesChanged(node, nsnull, stateMask);
           }
diff --git a/widget/src/cocoa/nsNativeThemeCocoa.h b/widget/src/cocoa/nsNativeThemeCocoa.h
index 98340b3354be..7aabaaa298a6 100644
--- a/widget/src/cocoa/nsNativeThemeCocoa.h
+++ b/widget/src/cocoa/nsNativeThemeCocoa.h
@@ -103,34 +103,35 @@ protected:
 
   // HITheme drawing routines
   void DrawFrame(CGContextRef context, HIThemeFrameKind inKind,
-                 const HIRect& inBoxRect, PRBool inReadOnly, PRInt32 inState);
+                 const HIRect& inBoxRect, PRBool inReadOnly,
+                 nsEventStates inState);
   void DrawProgress(CGContextRef context, const HIRect& inBoxRect,
                     PRBool inIsIndeterminate, PRBool inIsHorizontal,
                     PRInt32 inValue, PRInt32 inMaxValue, nsIFrame* aFrame);
-  void DrawTab(CGContextRef context, HIRect inBoxRect, PRInt32 inState,
+  void DrawTab(CGContextRef context, HIRect inBoxRect, nsEventStates inState,
                nsIFrame* aFrame);
   void DrawTabPanel(CGContextRef context, const HIRect& inBoxRect, nsIFrame* aFrame);
   void DrawScale(CGContextRef context, const HIRect& inBoxRect,
-                 PRInt32 inState, PRBool inDirection, PRBool inIsReverse,
-                 PRInt32 inCurrentValue, PRInt32 inMinValue, PRInt32 inMaxValue,
-                 nsIFrame* aFrame);
+                 nsEventStates inState, PRBool inDirection,
+                 PRBool inIsReverse, PRInt32 inCurrentValue, PRInt32 inMinValue,
+                 PRInt32 inMaxValue, nsIFrame* aFrame);
   void DrawCheckboxOrRadio(CGContextRef cgContext, PRBool inCheckbox,
                            const HIRect& inBoxRect, PRBool inSelected,
-                           PRInt32 inState, nsIFrame* aFrame);
+                           nsEventStates inState, nsIFrame* aFrame);
   void DrawSearchField(CGContextRef cgContext, const HIRect& inBoxRect,
-                       nsIFrame* aFrame, PRInt32 inState);
+                       nsIFrame* aFrame, nsEventStates inState);
   void DrawPushButton(CGContextRef cgContext, const HIRect& inBoxRect,
-                      PRInt32 inState, nsIFrame* aFrame);
+                      nsEventStates inState, nsIFrame* aFrame);
   void DrawButton(CGContextRef context, ThemeButtonKind inKind,
                   const HIRect& inBoxRect, PRBool inIsDefault, 
                   ThemeButtonValue inValue, ThemeButtonAdornment inAdornment,
-                  PRInt32 inState, nsIFrame* aFrame);
-  void DrawDropdown(CGContextRef context, const HIRect& inBoxRect, PRInt32 inState,
-                    PRUint8 aWidgetType, nsIFrame* aFrame);
+                  nsEventStates inState, nsIFrame* aFrame);
+  void DrawDropdown(CGContextRef context, const HIRect& inBoxRect,
+                    nsEventStates inState, PRUint8 aWidgetType,
+                    nsIFrame* aFrame);
   void DrawSpinButtons(CGContextRef context, ThemeButtonKind inKind,
-                       const HIRect& inBoxRect,
-                       ThemeDrawState inDrawState,
-                       ThemeButtonAdornment inAdornment, PRInt32 inState,
+                       const HIRect& inBoxRect, ThemeDrawState inDrawState,
+                       ThemeButtonAdornment inAdornment, nsEventStates inState,
                        nsIFrame* aFrame);
   void DrawUnifiedToolbar(CGContextRef cgContext, const HIRect& inBoxRect,
                           NSWindow* aWindow);
@@ -140,7 +141,7 @@ protected:
 
   // Scrollbars
   void DrawScrollbar(CGContextRef aCGContext, const HIRect& aBoxRect, nsIFrame *aFrame);
-  void GetScrollbarPressStates (nsIFrame *aFrame, PRInt32 aButtonStates[]);
+  void GetScrollbarPressStates (nsIFrame *aFrame, nsEventStates aButtonStates[]);
   void GetScrollbarDrawInfo (HIThemeTrackDrawInfo& aTdi, nsIFrame *aFrame, 
                              const CGSize& aSize, PRBool aShouldGetButtonStates);
   nsIFrame* GetParentScrollbarFrame(nsIFrame *aFrame);
diff --git a/widget/src/cocoa/nsNativeThemeCocoa.mm b/widget/src/cocoa/nsNativeThemeCocoa.mm
index 075dec708c96..32ffed59bd0e 100644
--- a/widget/src/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/src/cocoa/nsNativeThemeCocoa.mm
@@ -610,7 +610,7 @@ static const CellRenderSettings checkboxSettings = {
 void
 nsNativeThemeCocoa::DrawCheckboxOrRadio(CGContextRef cgContext, PRBool inCheckbox,
                                         const HIRect& inBoxRect, PRBool inSelected,
-                                        PRInt32 inState, nsIFrame* aFrame)
+                                        nsEventStates inState, nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -622,9 +622,9 @@ nsNativeThemeCocoa::DrawCheckboxOrRadio(CGContextRef cgContext, PRBool inCheckbo
     state = NSMixedState;
 
   [cell setEnabled:!IsDisabled(aFrame, inState)];
-  [cell setShowsFirstResponder:(inState & NS_EVENT_STATE_FOCUS)];
+  [cell setShowsFirstResponder:inState.HasState(NS_EVENT_STATE_FOCUS)];
   [cell setState:state];
-  [cell setHighlighted:((inState & NS_EVENT_STATE_ACTIVE) && (inState & NS_EVENT_STATE_HOVER))];
+  [cell setHighlighted:inState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER)];
   [cell setControlTint:(FrameIsInActiveWindow(aFrame) ? [NSColor currentControlTint] : NSClearControlTint)];
 
   // Ensure that the control is square.
@@ -667,7 +667,7 @@ static const CellRenderSettings searchFieldSettings = {
 
 void
 nsNativeThemeCocoa::DrawSearchField(CGContextRef cgContext, const HIRect& inBoxRect,
-                                    nsIFrame* aFrame, PRInt32 inState)
+                                    nsIFrame* aFrame, nsEventStates inState)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -715,7 +715,7 @@ static const CellRenderSettings pushButtonSettings = {
 
 void
 nsNativeThemeCocoa::DrawPushButton(CGContextRef cgContext, const HIRect& inBoxRect,
-                                   PRInt32 inState, nsIFrame* aFrame)
+                                   nsEventStates inState, nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -723,10 +723,9 @@ nsNativeThemeCocoa::DrawPushButton(CGContextRef cgContext, const HIRect& inBoxRe
   BOOL isDisabled = IsDisabled(aFrame, inState);
 
   [mPushButtonCell setEnabled:!isDisabled];
-  [mPushButtonCell setHighlighted:((inState & NS_EVENT_STATE_ACTIVE) &&
-                                   (inState & NS_EVENT_STATE_HOVER) && 
-                                   isActive)];
-  [mPushButtonCell setShowsFirstResponder:(inState & NS_EVENT_STATE_FOCUS) && !isDisabled && isActive];
+  [mPushButtonCell setHighlighted:isActive &&
+                                  inState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER)];
+  [mPushButtonCell setShowsFirstResponder:inState.HasState(NS_EVENT_STATE_FOCUS) && !isDisabled && isActive];
 
   // If the button is tall enough, draw the square button style so that buttons with
   // non-standard content look good. Otherwise draw normal rounded aqua buttons.
@@ -831,7 +830,7 @@ void
 nsNativeThemeCocoa::DrawButton(CGContextRef cgContext, ThemeButtonKind inKind,
                                const HIRect& inBoxRect, PRBool inIsDefault,
                                ThemeButtonValue inValue, ThemeButtonAdornment inAdornment,
-                               PRInt32 inState, nsIFrame* aFrame)
+                               nsEventStates inState, nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -847,7 +846,7 @@ nsNativeThemeCocoa::DrawButton(CGContextRef cgContext, ThemeButtonKind inKind,
   if (isDisabled) {
     bdi.state = kThemeStateUnavailable;
   }
-  else if ((inState & NS_EVENT_STATE_ACTIVE) && (inState & NS_EVENT_STATE_HOVER)) {
+  else if (inState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER)) {
     bdi.state = kThemeStatePressed;
   }
   else {
@@ -859,11 +858,11 @@ nsNativeThemeCocoa::DrawButton(CGContextRef cgContext, ThemeButtonKind inKind,
       bdi.state = kThemeStateActive;
   }
 
-  if (inState & NS_EVENT_STATE_FOCUS && isActive)
+  if (inState.HasState(NS_EVENT_STATE_FOCUS) && isActive)
     bdi.adornment |= kThemeAdornmentFocus;
 
   if (inIsDefault && !isDisabled && isActive &&
-      !(inState & NS_EVENT_STATE_ACTIVE)) {
+      !inState.HasState(NS_EVENT_STATE_ACTIVE)) {
     bdi.adornment |= kThemeAdornmentDefault;
     bdi.animation.time.start = 0;
     bdi.animation.time.current = CFAbsoluteTimeGetCurrent();
@@ -960,7 +959,8 @@ static const CellRenderSettings editableMenulistSettings = {
 
 void
 nsNativeThemeCocoa::DrawDropdown(CGContextRef cgContext, const HIRect& inBoxRect,
-                                 PRInt32 inState, PRUint8 aWidgetType, nsIFrame* aFrame)
+                                 nsEventStates inState, PRUint8 aWidgetType,
+                                 nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -970,7 +970,7 @@ nsNativeThemeCocoa::DrawDropdown(CGContextRef cgContext, const HIRect& inBoxRect
   NSCell* cell = isEditable ? (NSCell*)mComboBoxCell : (NSCell*)mDropdownCell;
 
   [cell setEnabled:!IsDisabled(aFrame, inState)];
-  [cell setShowsFirstResponder:(IsFocused(aFrame) || (inState & NS_EVENT_STATE_FOCUS))];
+  [cell setShowsFirstResponder:(IsFocused(aFrame) || inState.HasState(NS_EVENT_STATE_FOCUS))];
   [cell setHighlighted:IsOpenButton(aFrame)];
   [cell setControlTint:(FrameIsInActiveWindow(aFrame) ? [NSColor currentControlTint] : NSClearControlTint)];
 
@@ -985,7 +985,7 @@ void
 nsNativeThemeCocoa::DrawSpinButtons(CGContextRef cgContext, ThemeButtonKind inKind,
                                     const HIRect& inBoxRect, ThemeDrawState inDrawState,
                                     ThemeButtonAdornment inAdornment,
-                                    PRInt32 inState, nsIFrame* aFrame)
+                                    nsEventStates inState, nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -1007,7 +1007,8 @@ nsNativeThemeCocoa::DrawSpinButtons(CGContextRef cgContext, ThemeButtonKind inKi
 
 void
 nsNativeThemeCocoa::DrawFrame(CGContextRef cgContext, HIThemeFrameKind inKind,
-                              const HIRect& inBoxRect, PRBool inDisabled, PRInt32 inState)
+                              const HIRect& inBoxRect, PRBool inDisabled,
+                              nsEventStates inState)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -1023,7 +1024,7 @@ nsNativeThemeCocoa::DrawFrame(CGContextRef cgContext, HIThemeFrameKind inKind,
   if (inKind == kHIThemeFrameListBox)
     fdi.isFocused = 0;
   else
-    fdi.isFocused = (inState & NS_EVENT_STATE_FOCUS) != 0;
+    fdi.isFocused = inState.HasState(NS_EVENT_STATE_FOCUS);
 
   // HIThemeDrawFrame takes the rect for the content area of the frame, not
   // the bounding rect for the frame. Here we reduce the size of the rect we
@@ -1115,7 +1116,7 @@ nsNativeThemeCocoa::DrawTabPanel(CGContextRef cgContext, const HIRect& inBoxRect
 
 void
 nsNativeThemeCocoa::DrawScale(CGContextRef cgContext, const HIRect& inBoxRect,
-                              PRInt32 inState, PRBool inIsVertical,
+                              nsEventStates inState, PRBool inIsVertical,
                               PRBool inIsReverse, PRInt32 inCurrentValue,
                               PRInt32 inMinValue, PRInt32 inMaxValue,
                               nsIFrame* aFrame)
@@ -1135,7 +1136,7 @@ nsNativeThemeCocoa::DrawScale(CGContextRef cgContext, const HIRect& inBoxRect,
     tdi.attributes |= kThemeTrackHorizontal;
   if (inIsReverse)
     tdi.attributes |= kThemeTrackRightToLeft;
-  if (inState & NS_EVENT_STATE_FOCUS)
+  if (inState.HasState(NS_EVENT_STATE_FOCUS))
     tdi.attributes |= kThemeTrackHasFocus;
   if (IsDisabled(aFrame, inState))
     tdi.enableState = kThemeTrackDisabled;
@@ -1155,7 +1156,7 @@ nsNativeThemeCocoa::DrawScale(CGContextRef cgContext, const HIRect& inBoxRect,
 
 void
 nsNativeThemeCocoa::DrawTab(CGContextRef cgContext, HIRect inBoxRect,
-                            PRInt32 inState, nsIFrame* aFrame)
+                            nsEventStates inState, nsIFrame* aFrame)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
@@ -1174,7 +1175,7 @@ nsNativeThemeCocoa::DrawTab(CGContextRef cgContext, HIRect inBoxRect,
   } else {
     if (isDisabled)
       tdi.style = kThemeTabNonFrontUnavailable;
-    else if ((inState & NS_EVENT_STATE_ACTIVE) && (inState & NS_EVENT_STATE_HOVER))
+    else if (inState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER))
       tdi.style = kThemeTabNonFrontPressed;
     else
       tdi.style = FrameIsInActiveWindow(aFrame) ? kThemeTabNonFront : kThemeTabNonFrontInactive;
@@ -1223,7 +1224,7 @@ nsNativeThemeCocoa::DrawTab(CGContextRef cgContext, HIRect inBoxRect,
     inBoxRect.size.width += 1;
   }
   
-  if (inState & NS_EVENT_STATE_FOCUS)
+  if (inState.HasState(NS_EVENT_STATE_FOCUS))
     tdi.adornment |= kThemeAdornmentFocus;
 
   HIThemeDrawTab(&inBoxRect, &tdi, cgContext, HITHEME_ORIENTATION, NULL);
@@ -1232,14 +1233,14 @@ nsNativeThemeCocoa::DrawTab(CGContextRef cgContext, HIRect inBoxRect,
 }
 
 static inline UInt8
-ConvertToPressState(PRInt32 aButtonState, UInt8 aPressState)
+ConvertToPressState(nsEventStates aButtonState, UInt8 aPressState)
 {
   // If the button is pressed, return the press state passed in. Otherwise, return 0.
-  return ((aButtonState & NS_EVENT_STATE_ACTIVE) && (aButtonState & NS_EVENT_STATE_HOVER)) ? aPressState : 0;
+  return aButtonState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER) ? aPressState : 0;
 }
 
 void 
-nsNativeThemeCocoa::GetScrollbarPressStates(nsIFrame *aFrame, PRInt32 aButtonStates[])
+nsNativeThemeCocoa::GetScrollbarPressStates(nsIFrame *aFrame, nsEventStates aButtonStates[])
 {
   static nsIContent::AttrValuesArray attributeValues[] = {
     &nsWidgetAtoms::scrollbarUpTop,
@@ -1260,8 +1261,7 @@ nsNativeThemeCocoa::GetScrollbarPressStates(nsIFrame *aFrame, PRInt32 aButtonSta
                                                       attributeValues, eCaseMatters);
     if (attrIndex < 0) continue;
 
-    PRInt32 currentState = GetContentState(childFrame, NS_THEME_BUTTON);
-    aButtonStates[attrIndex] = currentState;
+    aButtonStates[attrIndex] = GetContentState(childFrame, NS_THEME_BUTTON);
   }
 }
 
@@ -1325,7 +1325,7 @@ nsNativeThemeCocoa::GetScrollbarDrawInfo(HIThemeTrackDrawInfo& aTdi, nsIFrame *a
   // Only go get these scrollbar button states if we need it. For example, there's no reaon to look up scrollbar button 
   // states when we're only creating a TrackDrawInfo to determine the size of the thumb.
   if (aShouldGetButtonStates) {
-    PRInt32 buttonStates[] = {0, 0, 0, 0};
+    nsEventStates buttonStates[4];
     GetScrollbarPressStates(aFrame, buttonStates);
     NSString *buttonPlacement = [[NSUserDefaults standardUserDefaults] objectForKey:@"AppleScrollBarVariant"];
     // It seems that unless all four buttons are showing, kThemeTopOutsideArrowPressed is the correct constant for
@@ -1601,7 +1601,7 @@ nsNativeThemeCocoa::DrawWidgetBackground(nsIRenderingContext* aContext, nsIFrame
   //CGContextFillRect(cgContext, bounds);
 #endif
 
-  PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+  nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
   switch (aWidgetType) {
     case NS_THEME_DIALOG: {
@@ -1927,7 +1927,7 @@ nsNativeThemeCocoa::DrawWidgetBackground(nsIRenderingContext* aContext, nsIFrame
       CGContextStrokePath(cgContext);
 
       // draw a focus ring
-      if (eventState & NS_EVENT_STATE_FOCUS) {
+      if (eventState.HasState(NS_EVENT_STATE_FOCUS)) {
         // We need to bring the rectangle in by 1 pixel on each side.
         CGRect cgr = CGRectMake(macRect.origin.x + 1,
                                 macRect.origin.y + 1,
diff --git a/widget/src/gtk2/nsNativeThemeGTK.cpp b/widget/src/gtk2/nsNativeThemeGTK.cpp
index 1ce0573893da..d5206e7f1da0 100644
--- a/widget/src/gtk2/nsNativeThemeGTK.cpp
+++ b/widget/src/gtk2/nsNativeThemeGTK.cpp
@@ -255,12 +255,12 @@ nsNativeThemeGTK::GetGtkWidgetAndState(PRUint8 aWidgetType, nsIFrame* aFrame,
         stateFrame = aFrame = aFrame->GetParent();
       }
 
-      PRInt32 eventState = GetContentState(stateFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(stateFrame, aWidgetType);
 
       aState->disabled = IsDisabled(aFrame, eventState) || IsReadOnly(aFrame);
-      aState->active  = (eventState & NS_EVENT_STATE_ACTIVE) == NS_EVENT_STATE_ACTIVE;
-      aState->focused = (eventState & NS_EVENT_STATE_FOCUS) == NS_EVENT_STATE_FOCUS;
-      aState->inHover = (eventState & NS_EVENT_STATE_HOVER) == NS_EVENT_STATE_HOVER;
+      aState->active  = eventState.HasState(NS_EVENT_STATE_ACTIVE);
+      aState->focused = eventState.HasState(NS_EVENT_STATE_FOCUS);
+      aState->inHover = eventState.HasState(NS_EVENT_STATE_HOVER);
       aState->isDefault = IsDefaultButton(aFrame);
       aState->canDefault = FALSE; // XXX fix me
       aState->depressed = FALSE;
diff --git a/widget/src/qt/nsNativeThemeQt.cpp b/widget/src/qt/nsNativeThemeQt.cpp
index 9f87cea8b303..8b6d395b90de 100644
--- a/widget/src/qt/nsNativeThemeQt.cpp
+++ b/widget/src/qt/nsNativeThemeQt.cpp
@@ -314,7 +314,7 @@ nsNativeThemeQt::DrawWidgetBackground(QPainter *qPainter,
     case NS_THEME_TEXTFIELD_MULTILINE:
     case NS_THEME_LISTBOX: {
         QStyleOptionFrameV2 frameOpt;
-        PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+        nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
         if (!IsDisabled(aFrame, eventState))
             frameOpt.state |= QStyle::State_Enabled;
@@ -638,7 +638,7 @@ nsNativeThemeQt::InitButtonStyle(PRUint8 aWidgetType,
                                  QRect rect,
                                  QStyleOptionButton &opt)
 {
-    PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+    nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
     opt.rect = rect;
     opt.palette = mNoBackgroundPalette;
@@ -647,11 +647,11 @@ nsNativeThemeQt::InitButtonStyle(PRUint8 aWidgetType,
 
     if (!isDisabled)
         opt.state |= QStyle::State_Enabled;
-    if (eventState & NS_EVENT_STATE_HOVER)
+    if (eventState.HasState(NS_EVENT_STATE_HOVER))
         opt.state |= QStyle::State_MouseOver;
-    if (eventState & NS_EVENT_STATE_FOCUS)
+    if (eventState.HasState(NS_EVENT_STATE_FOCUS))
         opt.state |= QStyle::State_HasFocus;
-    if (!isDisabled && (eventState & NS_EVENT_STATE_ACTIVE))
+    if (!isDisabled && eventState.HasState(NS_EVENT_STATE_ACTIVE))
         // Don't allow sunken when disabled
         opt.state |= QStyle::State_Sunken;
 
@@ -665,7 +665,7 @@ nsNativeThemeQt::InitButtonStyle(PRUint8 aWidgetType,
 
         break;
     default:
-        if (!(eventState & NS_EVENT_STATE_ACTIVE))
+        if (!eventState.HasState(NS_EVENT_STATE_ACTIVE))
             opt.state |= QStyle::State_Raised;
         break;
     }
@@ -678,15 +678,15 @@ nsNativeThemeQt::InitPlainStyle(PRUint8 aWidgetType,
                                 QStyleOption &opt,
                                 QStyle::State extraFlags)
 {
-    PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+    nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
     opt.rect = rect;
 
     if (!IsDisabled(aFrame, eventState))
         opt.state |= QStyle::State_Enabled;
-    if (eventState & NS_EVENT_STATE_HOVER)
+    if (eventState.HasState(NS_EVENT_STATE_HOVER))
         opt.state |= QStyle::State_MouseOver;
-    if (eventState & NS_EVENT_STATE_FOCUS)
+    if (eventState.HasState(NS_EVENT_STATE_FOCUS))
         opt.state |= QStyle::State_HasFocus;
 
     opt.state |= extraFlags;
@@ -698,18 +698,18 @@ nsNativeThemeQt::InitComboStyle(PRUint8 aWidgetType,
                                 QRect rect,
                                 QStyleOptionComboBox &opt)
 {
-    PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+    nsEventStates eventState = GetContentState(aFrame, aWidgetType);
     PRBool isDisabled = IsDisabled(aFrame, eventState);
 
     if (!isDisabled)
         opt.state |= QStyle::State_Enabled;
-    if (eventState & NS_EVENT_STATE_HOVER)
+    if (eventState.HasState(NS_EVENT_STATE_HOVER))
         opt.state |= QStyle::State_MouseOver;
-    if (eventState & NS_EVENT_STATE_FOCUS)
+    if (eventState.HasState(NS_EVENT_STATE_FOCUS))
         opt.state |= QStyle::State_HasFocus;
-    if (!(eventState & NS_EVENT_STATE_ACTIVE))
+    if (!eventState.HasState(NS_EVENT_STATE_ACTIVE))
         opt.state |= QStyle::State_Raised;
-    if (!isDisabled && (eventState & NS_EVENT_STATE_ACTIVE))
+    if (!isDisabled && eventState.HasState(NS_EVENT_STATE_ACTIVE))
         // Don't allow sunken when disabled
         opt.state |= QStyle::State_Sunken;
 
diff --git a/widget/src/windows/nsNativeThemeWin.cpp b/widget/src/windows/nsNativeThemeWin.cpp
index 9a330e3f8da7..f24998bbd97e 100644
--- a/widget/src/windows/nsNativeThemeWin.cpp
+++ b/widget/src/windows/nsNativeThemeWin.cpp
@@ -137,28 +137,28 @@ static PRInt32 GetTopLevelWindowActiveState(nsIFrame *aFrame)
   return mozilla::widget::themeconst::FS_INACTIVE;
 }
 
-static PRInt32 GetWindowFrameButtonState(nsIFrame *aFrame, PRInt32 eventState)
+static PRInt32 GetWindowFrameButtonState(nsIFrame *aFrame, nsEventStates eventState)
 {
   if (GetTopLevelWindowActiveState(aFrame) ==
       mozilla::widget::themeconst::FS_INACTIVE) {
-    if (eventState & NS_EVENT_STATE_HOVER)
+    if (eventState.HasState(NS_EVENT_STATE_HOVER))
       return mozilla::widget::themeconst::BS_HOT;
     return mozilla::widget::themeconst::BS_INACTIVE;
   }
 
-  if (eventState & NS_EVENT_STATE_ACTIVE)
+  if (eventState.HasState(NS_EVENT_STATE_ACTIVE))
     return mozilla::widget::themeconst::BS_PUSHED;
-  else if (eventState & NS_EVENT_STATE_HOVER)
+  else if (eventState.HasState(NS_EVENT_STATE_HOVER))
     return mozilla::widget::themeconst::BS_HOT;
   else
     return mozilla::widget::themeconst::BS_NORMAL;
 }
 
-static PRInt32 GetClassicWindowFrameButtonState(PRInt32 eventState)
+static PRInt32 GetClassicWindowFrameButtonState(nsEventStates eventState)
 {
-  if (eventState & NS_EVENT_STATE_ACTIVE)
+  if (eventState.HasState(NS_EVENT_STATE_ACTIVE))
     return DFCS_BUTTONPUSH|DFCS_PUSHED;
-  else if (eventState & NS_EVENT_STATE_HOVER)
+  else if (eventState.HasState(NS_EVENT_STATE_HOVER))
     return DFCS_BUTTONPUSH|DFCS_HOT;
   else
     return DFCS_BUTTONPUSH;
@@ -440,12 +440,12 @@ PRInt32
 nsNativeThemeWin::StandardGetState(nsIFrame* aFrame, PRUint8 aWidgetType,
                                    PRBool wantFocused)
 {
-  PRInt32 eventState = GetContentState(aFrame, aWidgetType);
-  if (eventState & NS_EVENT_STATE_HOVER && eventState & NS_EVENT_STATE_ACTIVE)
+  nsEventStates eventState = GetContentState(aFrame, aWidgetType);
+  if (eventState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
     return TS_ACTIVE;
-  if (wantFocused && eventState & NS_EVENT_STATE_FOCUS)
+  if (wantFocused && eventState.HasState(NS_EVENT_STATE_FOCUS))
     return TS_FOCUSED;
-  if (eventState & NS_EVENT_STATE_HOVER)
+  if (eventState.HasState(NS_EVENT_STATE_HOVER))
     return TS_HOVER;
 
   return TS_NORMAL;
@@ -487,7 +487,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
         return NS_OK;
       }
 
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (IsDisabled(aFrame, eventState)) {
         aState = TS_DISABLED;
         return NS_OK;
@@ -525,8 +525,8 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
           inputState = INDETERMINATE;
         }
 
-        PRInt32 eventState = GetContentState(isXULCheckboxRadio ? aFrame->GetParent()
-                                                                : aFrame,
+        nsEventStates eventState = GetContentState(isXULCheckboxRadio ? aFrame->GetParent()
+                                                                      : aFrame,
                                              aWidgetType);
         if (IsDisabled(aFrame, eventState)) {
           aState = TS_DISABLED;
@@ -548,7 +548,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     }
     case NS_THEME_TEXTFIELD:
     case NS_THEME_TEXTFIELD_MULTILINE: {
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       if (nsUXThemeData::sIsVistaOrLater) {
         /* Note: the NOSCROLL type has a rounded corner in each
@@ -576,9 +576,9 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
            */
           if (content && content->IsXUL() && IsFocused(aFrame))
             aState = TFS_EDITBORDER_FOCUSED;
-          else if (eventState & NS_EVENT_STATE_ACTIVE || eventState & NS_EVENT_STATE_FOCUS)
+          else if (eventState.HasAtLeastOneOfStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_FOCUS))
             aState = TFS_EDITBORDER_FOCUSED;
-          else if (eventState & NS_EVENT_STATE_HOVER)
+          else if (eventState.HasState(NS_EVENT_STATE_HOVER))
             aState = TFS_EDITBORDER_HOVER;
           else
             aState = TFS_EDITBORDER_NORMAL;
@@ -630,7 +630,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
         return NS_OK;
       }
 
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (IsDisabled(aFrame, eventState)) {
         aState = TS_DISABLED;
         return NS_OK;
@@ -640,9 +640,9 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
         return NS_OK;
       }
 
-      if (eventState & NS_EVENT_STATE_HOVER && eventState & NS_EVENT_STATE_ACTIVE)
+      if (eventState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
         aState = TS_ACTIVE;
-      else if (eventState & NS_EVENT_STATE_HOVER) {
+      else if (eventState.HasState(NS_EVENT_STATE_HOVER)) {
         if (IsCheckedButton(aFrame))
           aState = TB_HOVER_CHECKED;
         else
@@ -668,19 +668,19 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_SCROLLBAR_BUTTON_RIGHT: {
       aPart = SP_BUTTON;
       aState = (aWidgetType - NS_THEME_SCROLLBAR_BUTTON_UP)*4;
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (!aFrame)
         aState += TS_NORMAL;
       else if (IsDisabled(aFrame, eventState))
         aState += TS_DISABLED;
       else {
         nsIFrame *parent = aFrame->GetParent();
-        PRInt32 parentState = GetContentState(parent, parent->GetStyleDisplay()->mAppearance);
-        if (eventState & NS_EVENT_STATE_HOVER && eventState & NS_EVENT_STATE_ACTIVE)
+        nsEventStates parentState = GetContentState(parent, parent->GetStyleDisplay()->mAppearance);
+        if (eventState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
           aState += TS_ACTIVE;
-        else if (eventState & NS_EVENT_STATE_HOVER)
+        else if (eventState.HasState(NS_EVENT_STATE_HOVER))
           aState += TS_HOVER;
-        else if (nsUXThemeData::sIsVistaOrLater && parentState & NS_EVENT_STATE_HOVER)
+        else if (nsUXThemeData::sIsVistaOrLater && parentState.HasState(NS_EVENT_STATE_HOVER))
           aState = (aWidgetType - NS_THEME_SCROLLBAR_BUTTON_UP) + SP_BUTTON_IMPLICIT_HOVER_BASE;
         else
           aState += TS_NORMAL;
@@ -698,17 +698,17 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_SCROLLBAR_THUMB_VERTICAL: {
       aPart = (aWidgetType == NS_THEME_SCROLLBAR_THUMB_HORIZONTAL) ?
               SP_THUMBHOR : SP_THUMBVERT;
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (!aFrame)
         aState = TS_NORMAL;
       else if (IsDisabled(aFrame, eventState))
         aState = TS_DISABLED;
       else {
-        if (eventState & NS_EVENT_STATE_ACTIVE) // Hover is not also a requirement for
-                                                // the thumb, since the drag is not canceled
-                                                // when you move outside the thumb.
+        if (eventState.HasState(NS_EVENT_STATE_ACTIVE)) // Hover is not also a requirement for
+                                                        // the thumb, since the drag is not canceled
+                                                        // when you move outside the thumb.
           aState = TS_ACTIVE;
-        else if (eventState & NS_EVENT_STATE_HOVER)
+        else if (eventState.HasState(NS_EVENT_STATE_HOVER))
           aState = TS_HOVER;
         else 
           aState = TS_NORMAL;
@@ -727,20 +727,20 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_SCALE_THUMB_VERTICAL: {
       aPart = (aWidgetType == NS_THEME_SCALE_THUMB_HORIZONTAL) ?
               TKP_THUMB : TKP_THUMBVERT;
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (!aFrame)
         aState = TS_NORMAL;
       else if (IsDisabled(aFrame, eventState)) {
         aState = TKP_DISABLED;
       }
       else {
-        if (eventState & NS_EVENT_STATE_ACTIVE) // Hover is not also a requirement for
-                                                // the thumb, since the drag is not canceled
-                                                // when you move outside the thumb.
+        if (eventState.HasState(NS_EVENT_STATE_ACTIVE)) // Hover is not also a requirement for
+                                                        // the thumb, since the drag is not canceled
+                                                        // when you move outside the thumb.
           aState = TS_ACTIVE;
-        else if (eventState & NS_EVENT_STATE_FOCUS)
+        else if (eventState.HasState(NS_EVENT_STATE_FOCUS))
           aState = TKP_FOCUSED;
-        else if (eventState & NS_EVENT_STATE_HOVER)
+        else if (eventState.HasState(NS_EVENT_STATE_HOVER))
           aState = TS_HOVER;
         else
           aState = TS_NORMAL;
@@ -751,7 +751,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_SPINNER_DOWN_BUTTON: {
       aPart = (aWidgetType == NS_THEME_SPINNER_UP_BUTTON) ?
               SPNP_UP : SPNP_DOWN;
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (!aFrame)
         aState = TS_NORMAL;
       else if (IsDisabled(aFrame, eventState))
@@ -824,7 +824,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
         return NS_OK;
       }
 
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       if (IsDisabled(aFrame, eventState)) {
         aState = TS_DISABLED;
         return NS_OK;
@@ -859,7 +859,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_DROPDOWN: {
       nsIContent* content = aFrame->GetContent();
       PRBool isHTML = content && content->IsHTML();
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       /* On vista, in HTML, we use CBP_DROPBORDER instead of DROPFRAME for HTML content;
        * this gives us the thin outline in HTML content, instead of the gradient-filled
@@ -876,11 +876,11 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
       } else if (IsOpenButton(aFrame)) {
         aState = TS_ACTIVE;
       } else {
-        if (isHTML && eventState & NS_EVENT_STATE_FOCUS)
+        if (isHTML && eventState.HasState(NS_EVENT_STATE_FOCUS))
           aState = TS_ACTIVE;
-        else if (eventState & NS_EVENT_STATE_HOVER && eventState & NS_EVENT_STATE_ACTIVE)
+        else if (eventState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
           aState = TS_ACTIVE;
-        else if (eventState & NS_EVENT_STATE_HOVER)
+        else if (eventState.HasState(NS_EVENT_STATE_HOVER))
           aState = TS_HOVER;
         else
           aState = TS_NORMAL;
@@ -898,7 +898,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
       if (isHTML || isMenulist)
         aFrame = parentFrame;
 
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
       aPart = nsUXThemeData::sIsVistaOrLater ? CBP_DROPMARKER_VISTA : CBP_DROPMARKER;
 
       // For HTML controls with author styling, we should fall
@@ -946,7 +946,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
       aState = TS_NORMAL;
 
       // Dropdown button active state doesn't need :hover.
-      if (eventState & NS_EVENT_STATE_ACTIVE) {
+      if (eventState.HasState(NS_EVENT_STATE_ACTIVE)) {
         if (isOpen && (isHTML || isMenulist)) {
           // XXX Button should look active until the mouse is released, but
           //     without making it look active when the popup is clicked.
@@ -954,7 +954,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
         }
         aState = TS_ACTIVE;
       }
-      else if (eventState & NS_EVENT_STATE_HOVER) {
+      else if (eventState.HasState(NS_EVENT_STATE_HOVER)) {
         // No hover effect for XUL menulists and autocomplete dropdown buttons
         // while the dropdown menu is open.
         if (isOpen) {
@@ -978,7 +978,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
       PRBool isOpen = PR_FALSE;
       PRBool isHover = PR_FALSE;
       nsIMenuFrame *menuFrame = do_QueryFrame(aFrame);
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       isTopLevel = IsTopLevelMenu(aFrame);
 
@@ -1022,7 +1022,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_MENUARROW:
       {
         aPart = MENU_POPUPSUBMENU;
-        PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+        nsEventStates eventState = GetContentState(aFrame, aWidgetType);
         aState = IsDisabled(aFrame, eventState) ? MSM_DISABLED : MSM_NORMAL;
         return NS_OK;
       }
@@ -1030,7 +1030,7 @@ nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame, PRUint8 aWidgetType,
     case NS_THEME_MENURADIO:
       {
         PRBool isChecked;
-        PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+        nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
         // NOTE: we can probably use NS_EVENT_STATE_CHECKED
         isChecked = CheckBooleanAttr(aFrame, nsWidgetAtoms::checked);
@@ -1258,7 +1258,7 @@ RENDER_AGAIN:
       if (isChecked)
       {
         int bgState = MCB_NORMAL;
-        PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+        nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
         // the disabled states are offset by 1
         if (IsDisabled(aFrame, eventState))
@@ -1349,10 +1349,9 @@ RENDER_AGAIN:
         aFrame->GetContent()->IsHTML()) ||
       aWidgetType == NS_THEME_SCALE_HORIZONTAL ||
       aWidgetType == NS_THEME_SCALE_VERTICAL) {
-      PRInt32 contentState;
-      contentState = GetContentState(aFrame, aWidgetType);  
+      nsEventStates contentState = GetContentState(aFrame, aWidgetType);
 
-      if (contentState & NS_EVENT_STATE_FOCUS) {
+      if (contentState.HasState(NS_EVENT_STATE_FOCUS)) {
         POINT vpOrg;
         HPEN hPen = nsnull;
 
@@ -1375,7 +1374,7 @@ RENDER_AGAIN:
           ::SelectObject(hdc, hPen);
 
           // If pressed, draw the upper left corner of the dotted rect.
-          if (contentState & NS_EVENT_STATE_ACTIVE) {
+          if (contentState.HasState(NS_EVENT_STATE_ACTIVE)) {
             ::MoveToEx(hdc, widgetRect.left, widgetRect.bottom-1, NULL);
             ::LineTo(hdc, widgetRect.left, widgetRect.top);
             ::LineTo(hdc, widgetRect.right-1, widgetRect.top);
@@ -2489,7 +2488,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
 {  
   switch (aWidgetType) {
     case NS_THEME_BUTTON: {
-      PRInt32 contentState;
+      nsEventStates contentState;
 
       aPart = DFC_BUTTON;
       aState = DFCS_BUTTONPUSH;
@@ -2503,7 +2502,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
       else if (IsCheckedButton(aFrame))
         aState |= DFCS_CHECKED;
       else {
-        if (contentState & NS_EVENT_STATE_ACTIVE && contentState & NS_EVENT_STATE_HOVER) {
+        if (contentState.HasAllStates(NS_EVENT_STATE_ACTIVE | NS_EVENT_STATE_HOVER)) {
           aState |= DFCS_PUSHED;
           const nsStyleUserInterface *uiData = aFrame->GetStyleUserInterface();
           // The down state is flat if the button is focusable
@@ -2515,9 +2514,9 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
             aFocused = PR_TRUE;
           }
         }
-        if ((contentState & NS_EVENT_STATE_FOCUS) || 
-          (aState == DFCS_BUTTONPUSH && IsDefaultButton(aFrame))) {
-          aFocused = PR_TRUE;          
+        if (contentState.HasState(NS_EVENT_STATE_FOCUS) ||
+            (aState == DFCS_BUTTONPUSH && IsDefaultButton(aFrame))) {
+          aFocused = PR_TRUE;
         }
 
       }
@@ -2526,7 +2525,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
     }
     case NS_THEME_CHECKBOX:
     case NS_THEME_RADIO: {
-      PRInt32 contentState;
+      nsEventStates contentState;
       aFocused = PR_FALSE;
 
       aPart = DFC_BUTTON;
@@ -2552,14 +2551,14 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
 
       contentState = GetContentState(aFrame, aWidgetType);
       if (!content->IsXUL() &&
-          (contentState & NS_EVENT_STATE_FOCUS)) {
+          contentState.HasState(NS_EVENT_STATE_FOCUS)) {
         aFocused = PR_TRUE;
       }
 
       if (IsDisabled(aFrame, contentState)) {
         aState |= DFCS_INACTIVE;
-      } else if (contentState & NS_EVENT_STATE_ACTIVE &&
-                 contentState & NS_EVENT_STATE_HOVER) {
+      } else if (contentState.HasAllStates(NS_EVENT_STATE_ACTIVE |
+                                           NS_EVENT_STATE_HOVER)) {
         aState |= DFCS_PUSHED;
       }
 
@@ -2572,7 +2571,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
       PRBool isOpen = PR_FALSE;
       PRBool isContainer = PR_FALSE;
       nsIMenuFrame *menuFrame = do_QueryFrame(aFrame);
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       // We indicate top-level-ness using aPart. 0 is a normal menu item,
       // 1 is a top-level menu item. The state of the item is composed of
@@ -2607,7 +2606,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
     case NS_THEME_MENURADIO:
     case NS_THEME_MENUARROW: {
       aState = 0;
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       if (IsDisabled(aFrame, eventState))
         aState |= DFCS_INACTIVE;
@@ -2666,7 +2665,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
       if (isHTML || isMenulist)
         aFrame = parentFrame;
 
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       if (IsDisabled(aFrame, eventState)) {
         aState |= DFCS_INACTIVE;
@@ -2687,7 +2686,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
         return NS_OK;
 
       // Dropdown button active state doesn't need :hover.
-      if (eventState & NS_EVENT_STATE_ACTIVE)
+      if (eventState.HasState(NS_EVENT_STATE_ACTIVE))
         aState |= DFCS_PUSHED | DFCS_FLAT;
 #endif
 
@@ -2697,7 +2696,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
     case NS_THEME_SCROLLBAR_BUTTON_DOWN:
     case NS_THEME_SCROLLBAR_BUTTON_LEFT:
     case NS_THEME_SCROLLBAR_BUTTON_RIGHT: {
-      PRInt32 contentState = GetContentState(aFrame, aWidgetType);
+      nsEventStates contentState = GetContentState(aFrame, aWidgetType);
 
       aPart = DFC_SCROLL;
       switch (aWidgetType) {
@@ -2719,8 +2718,8 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
         aState |= DFCS_INACTIVE;
       else {
 #ifndef WINCE
-        if (contentState & NS_EVENT_STATE_HOVER && contentState & NS_EVENT_STATE_ACTIVE)
-          aState |= DFCS_PUSHED | DFCS_FLAT;      
+        if (contentState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
+          aState |= DFCS_PUSHED | DFCS_FLAT;
 #endif
       }
 
@@ -2728,7 +2727,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
     }
     case NS_THEME_SPINNER_UP_BUTTON:
     case NS_THEME_SPINNER_DOWN_BUTTON: {
-      PRInt32 contentState = GetContentState(aFrame, aWidgetType);
+      nsEventStates contentState = GetContentState(aFrame, aWidgetType);
 
       aPart = DFC_SCROLL;
       switch (aWidgetType) {
@@ -2743,7 +2742,7 @@ nsresult nsNativeThemeWin::ClassicGetThemePartAndState(nsIFrame* aFrame, PRUint8
       if (IsDisabled(aFrame, contentState))
         aState |= DFCS_INACTIVE;
       else {
-        if (contentState & NS_EVENT_STATE_HOVER && contentState & NS_EVENT_STATE_ACTIVE)
+        if (contentState.HasAllStates(NS_EVENT_STATE_HOVER | NS_EVENT_STATE_ACTIVE))
           aState |= DFCS_PUSHED;
       }
 
@@ -3072,7 +3071,7 @@ RENDER_AGAIN:
     case NS_THEME_DROPDOWN_TEXTFIELD: {
       // Draw inset edge
       ::DrawEdge(hdc, &widgetRect, EDGE_SUNKEN, BF_RECT | BF_ADJUST);
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       // Fill in background
       if (IsDisabled(aFrame, eventState) ||
@@ -3135,7 +3134,7 @@ RENDER_AGAIN:
       break;
     case NS_THEME_SCALE_THUMB_VERTICAL:
     case NS_THEME_SCALE_THUMB_HORIZONTAL: {
-      PRInt32 eventState = GetContentState(aFrame, aWidgetType);
+      nsEventStates eventState = GetContentState(aFrame, aWidgetType);
 
       ::DrawEdge(hdc, &widgetRect, EDGE_RAISED, BF_RECT | BF_SOFT | BF_MIDDLE | BF_ADJUST);
       if (IsDisabled(aFrame, eventState)) {
diff --git a/widget/src/xpwidgets/nsNativeTheme.cpp b/widget/src/xpwidgets/nsNativeTheme.cpp
index 2150b4c74a87..ad7ffbd785d0 100644
--- a/widget/src/xpwidgets/nsNativeTheme.cpp
+++ b/widget/src/xpwidgets/nsNativeTheme.cpp
@@ -68,11 +68,11 @@ nsNativeTheme::GetPresShell(nsIFrame* aFrame)
   return context ? context->GetPresShell() : nsnull;
 }
 
-PRInt32
+nsEventStates
 nsNativeTheme::GetContentState(nsIFrame* aFrame, PRUint8 aWidgetType)
 {
   if (!aFrame)
-    return 0;
+    return nsEventStates();
 
   PRBool isXULCheckboxRadio = 
     (aWidgetType == NS_THEME_CHECKBOX ||
@@ -82,14 +82,14 @@ nsNativeTheme::GetContentState(nsIFrame* aFrame, PRUint8 aWidgetType)
     aFrame = aFrame->GetParent();
 
   if (!aFrame->GetContent())
-    return 0;
+    return nsEventStates();
 
   nsIPresShell *shell = GetPresShell(aFrame);
   if (!shell)
-    return 0;
+    return nsEventStates();
 
   nsIEventStateManager* esm = shell->GetPresContext()->EventStateManager();
-  PRInt32 flags = esm->GetContentState(aFrame->GetContent(), PR_TRUE);
+  nsEventStates flags = esm->GetContentState(aFrame->GetContent(), PR_TRUE);
   
   if (isXULCheckboxRadio && aWidgetType == NS_THEME_RADIO) {
     if (IsFocused(aFrame))
@@ -260,7 +260,7 @@ nsNativeTheme::IsWidgetStyled(nsPresContext* aPresContext, nsIFrame* aFrame,
 }
 
 bool
-nsNativeTheme::IsDisabled(nsIFrame* aFrame, PRInt32 aEventStates)
+nsNativeTheme::IsDisabled(nsIFrame* aFrame, nsEventStates aEventStates)
 {
   if (!aFrame) {
     return false;
@@ -272,7 +272,7 @@ nsNativeTheme::IsDisabled(nsIFrame* aFrame, PRInt32 aEventStates)
   }
 
   if (content->IsHTML()) {
-    return (aEventStates & NS_EVENT_STATE_DISABLED);
+    return aEventStates.HasState(NS_EVENT_STATE_DISABLED);
   }
 
   // For XML/XUL elements, an attribute must be equal to the literal
diff --git a/widget/src/xpwidgets/nsNativeTheme.h b/widget/src/xpwidgets/nsNativeTheme.h
index a0133d2afb11..af27b32b7b83 100644
--- a/widget/src/xpwidgets/nsNativeTheme.h
+++ b/widget/src/xpwidgets/nsNativeTheme.h
@@ -46,6 +46,7 @@
 #include "nsMargin.h"
 #include "nsILookAndFeel.h"
 #include "nsWidgetAtoms.h"
+#include "nsEventStates.h"
 
 class nsIFrame;
 class nsIPresShell;
@@ -70,7 +71,7 @@ class nsNativeTheme
   nsNativeTheme();
 
   // Returns the content state (hover, focus, etc), see nsIEventStateManager.h
-  PRInt32 GetContentState(nsIFrame* aFrame, PRUint8 aWidgetType);
+  nsEventStates GetContentState(nsIFrame* aFrame, PRUint8 aWidgetType);
 
   // Returns whether the widget is already styled by content
   // Normally called from ThemeSupportsWidget to turn off native theming
@@ -80,7 +81,7 @@ class nsNativeTheme
 
   // Accessors to widget-specific state information
 
-  bool IsDisabled(nsIFrame* aFrame, PRInt32 aEventStates);
+  bool IsDisabled(nsIFrame* aFrame, nsEventStates aEventStates);
 
   // RTL chrome direction
   PRBool IsFrameRTL(nsIFrame* aFrame);