diff --git a/content/base/src/nsNodeUtils.cpp b/content/base/src/nsNodeUtils.cpp
index 7c4f92d68356..a445076e107f 100644
--- a/content/base/src/nsNodeUtils.cpp
+++ b/content/base/src/nsNodeUtils.cpp
@@ -117,12 +117,11 @@ nsNodeUtils::AttributeWillChange(nsIContent* aContent,
 }
 
 void
-nsNodeUtils::AttributeChanged(nsIContent* aContent,
+nsNodeUtils::AttributeChanged(Element* aElement,
                               PRInt32 aNameSpaceID,
                               nsIAtom* aAttribute,
                               PRInt32 aModType)
 {
-  Element* aElement = aContent->AsElement();
   nsIDocument* doc = aElement->GetOwnerDoc();
   IMPL_MUTATION_NOTIFICATION(AttributeChanged, aElement,
                              (doc, aElement, aNameSpaceID, aAttribute,
diff --git a/content/base/src/nsNodeUtils.h b/content/base/src/nsNodeUtils.h
index 8931674ae09d..d4849a453d4b 100644
--- a/content/base/src/nsNodeUtils.h
+++ b/content/base/src/nsNodeUtils.h
@@ -85,13 +85,13 @@ public:
 
   /**
    * Send AttributeChanged notifications to nsIMutationObservers.
-   * @param aContent      Node whose data changed
+   * @param aElement      Element whose data changed
    * @param aNameSpaceID  Namespace of changed attribute
    * @param aAttribute    Local-name of changed attribute
    * @param aModType      Type of change (add/change/removal)
    * @see nsIMutationObserver::AttributeChanged
    */
-  static void AttributeChanged(nsIContent* aContent,
+  static void AttributeChanged(mozilla::dom::Element* aElement,
                                PRInt32 aNameSpaceID,
                                nsIAtom* aAttribute,
                                PRInt32 aModType);
diff --git a/layout/generic/nsFrameSetFrame.cpp b/layout/generic/nsFrameSetFrame.cpp
index b9566e71a5bc..5df6bb68d5a4 100644
--- a/layout/generic/nsFrameSetFrame.cpp
+++ b/layout/generic/nsFrameSetFrame.cpp
@@ -1,6 +1,5 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- *
- * ***** BEGIN LICENSE BLOCK *****
+/* -*- 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
@@ -70,7 +69,7 @@
 #include "nsCSSAnonBoxes.h"
 #include "nsAutoPtr.h"
 #include "nsStyleSet.h"
-#include "nsIContent.h"
+#include "mozilla/dom/Element.h"
 #include "nsDisplayList.h"
 #include "nsNodeUtils.h"
 #include "mozAutoDocUpdate.h"
@@ -270,7 +269,7 @@ nsHTMLFramesetFrame::FrameResizePrefCallback(const char* aPref, void* aClosure)
 
   frame->RecalculateBorderResize();
   if (doc) {
-    nsNodeUtils::AttributeChanged(frame->GetContent(),
+    nsNodeUtils::AttributeChanged(frame->GetContent()->AsElement(),
                                   kNameSpaceID_None,
                                   nsGkAtoms::frameborder,
                                   nsIDOMMutationEvent::MODIFICATION);
diff --git a/parser/html/nsHtml5TreeOperation.cpp b/parser/html/nsHtml5TreeOperation.cpp
index b9284f8609ef..e424494abea1 100644
--- a/parser/html/nsHtml5TreeOperation.cpp
+++ b/parser/html/nsHtml5TreeOperation.cpp
@@ -61,11 +61,14 @@
 #include "nsIFormProcessor.h"
 #include "nsIServiceManager.h"
 #include "nsEscape.h"
+#include "mozilla/dom/Element.h"
 
 #ifdef MOZ_SVG
 #include "nsHtml5SVGLoadDispatcher.h"
 #endif
 
+namespace dom = mozilla::dom;
+
 static NS_DEFINE_CID(kFormProcessorCID, NS_FORMPROCESSOR_CID);
 
 /**
@@ -313,7 +316,7 @@ nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
       return AppendToDocument(node, aBuilder);
     }
     case eTreeOpAddAttributes: {
-      nsIContent* node = *(mOne.node);
+      dom::Element* node = (*(mOne.node))->AsElement();
       nsHtml5HtmlAttributes* attributes = mTwo.attributes;
 
       nsHtml5OtherDocUpdate update(node->GetOwnerDoc(),
diff --git a/parser/html/nsHtml5TreeOperation.h b/parser/html/nsHtml5TreeOperation.h
index 699298de48c2..37b66aa97454 100644
--- a/parser/html/nsHtml5TreeOperation.h
+++ b/parser/html/nsHtml5TreeOperation.h
@@ -38,11 +38,11 @@
 #ifndef nsHtml5TreeOperation_h__
 #define nsHtml5TreeOperation_h__
 
-#include "nsIContent.h"
 #include "nsHtml5DocumentMode.h"
 #include "nsHtml5HtmlAttributes.h"
 #include "nsXPCOMStrings.h"
 
+class nsIContent;
 class nsHtml5TreeOpExecutor;
 class nsHtml5StateSnapshot;