diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 621ae98854ac..f7e0c1c9b96e 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -216,6 +216,8 @@
 #include "TabChild.h"
 #include "mozilla/dom/DocGroup.h"
 #include "mozilla/dom/TabGroup.h"
+#include "nsIWebNavigationInfo.h"
+#include "nsPluginHost.h"
 
 #include "nsIBidiKeyboard.h"
 
@@ -9988,3 +9990,93 @@ nsContentUtils::GetClosestNonNativeAnonymousAncestor(Element* aElement)
   }
   return e;
 }
+
+/**
+ * Checks whether the given type is a supported document type for
+ * loading within the nsObjectLoadingContent specified by aContent.
+ *
+ * NOTE Helper method for nsContentUtils::HtmlObjectContentTypeForMIMEType.
+ * NOTE Does not take content policy or capabilities into account
+ */
+static bool
+HtmlObjectContentSupportsDocument(const nsCString& aMimeType,
+                                  nsIContent* aContent)
+{
+  nsCOMPtr<nsIWebNavigationInfo> info(
+    do_GetService(NS_WEBNAVIGATION_INFO_CONTRACTID));
+  if (!info) {
+    return false;
+  }
+
+  nsCOMPtr<nsIWebNavigation> webNav;
+  if (aContent) {
+    nsIDocument* currentDoc = aContent->GetComposedDoc();
+    if (currentDoc) {
+      webNav = do_GetInterface(currentDoc->GetWindow());
+    }
+  }
+
+  uint32_t supported;
+  nsresult rv = info->IsTypeSupported(aMimeType, webNav, &supported);
+
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  if (supported != nsIWebNavigationInfo::UNSUPPORTED) {
+    // Don't want to support plugins as documents
+    return supported != nsIWebNavigationInfo::PLUGIN;
+  }
+
+  // Try a stream converter
+  // NOTE: We treat any type we can convert from as a supported type. If a
+  // type is not actually supported, the URI loader will detect that and
+  // return an error, and we'll fallback.
+  nsCOMPtr<nsIStreamConverterService> convServ =
+    do_GetService("@mozilla.org/streamConverters;1");
+  bool canConvert = false;
+  if (convServ) {
+    rv = convServ->CanConvert(aMimeType.get(), "*/*", &canConvert);
+  }
+  return NS_SUCCEEDED(rv) && canConvert;
+}
+
+/* static */ uint32_t
+nsContentUtils::HtmlObjectContentTypeForMIMEType(const nsCString& aMIMEType,
+                                                 nsIContent* aContent)
+{
+  if (aMIMEType.IsEmpty()) {
+    return nsIObjectLoadingContent::TYPE_NULL;
+  }
+
+  if (imgLoader::SupportImageWithMimeType(aMIMEType.get())) {
+    return nsIObjectLoadingContent::TYPE_IMAGE;
+  }
+
+  // Faking support of the PDF content as a document for EMBED tags
+  // when internal PDF viewer is enabled.
+  if (aMIMEType.LowerCaseEqualsLiteral("application/pdf") &&
+      IsPDFJSEnabled()) {
+    return nsIObjectLoadingContent::TYPE_DOCUMENT;
+  }
+
+  // Faking support of the SWF content as a document for EMBED tags
+  // when internal SWF player is enabled.
+  if (aMIMEType.LowerCaseEqualsLiteral("application/x-shockwave-flash") &&
+      IsSWFPlayerEnabled()) {
+    return nsIObjectLoadingContent::TYPE_DOCUMENT;
+  }
+
+  if (HtmlObjectContentSupportsDocument(aMIMEType, aContent)) {
+    return nsIObjectLoadingContent::TYPE_DOCUMENT;
+  }
+
+  RefPtr<nsPluginHost> pluginHost = nsPluginHost::GetInst();
+  if (pluginHost &&
+      pluginHost->HavePluginForType(aMIMEType, nsPluginHost::eExcludeNone)) {
+    // ShouldPlay will handle checking for disabled plugins
+    return nsIObjectLoadingContent::TYPE_PLUGIN;
+  }
+
+  return nsIObjectLoadingContent::TYPE_NULL;
+}
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index 9b2c83728f46..159343549fe6 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -2798,6 +2798,23 @@ public:
    */
   static Element* GetClosestNonNativeAnonymousAncestor(Element* aElement);
 
+  /**
+   * Returns one of the nsIObjectLoadingContent::TYPE_ values describing the
+   * content type which will be used for the given MIME type when loaded within
+   * an nsObjectLoadingContent.
+   *
+   * NOTE: This method doesn't take capabilities into account. The caller must
+   * take that into account.
+   *
+   * @param aMIMEType  The MIME type of the document being loaded.
+   * @param aContent The nsIContent object which is performing the load. May be
+   *                 nullptr in which case the docshell's plugin permissions
+   *                 will not be checked.
+   */
+  static uint32_t
+  HtmlObjectContentTypeForMIMEType(const nsCString& aMIMEType,
+                                   nsIContent* aContent);
+
 private:
   static bool InitializeEventTable();
 
diff --git a/dom/base/nsObjectLoadingContent.cpp b/dom/base/nsObjectLoadingContent.cpp
index 0649849bc7ad..3db7f038cc67 100644
--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -452,12 +452,6 @@ URIEquals(nsIURI *a, nsIURI *b)
   return (!a && !b) || (a && b && NS_SUCCEEDED(a->Equals(b, &equal)) && equal);
 }
 
-static bool
-IsSupportedImage(const nsCString& aMimeType)
-{
-  return imgLoader::SupportImageWithMimeType(aMimeType.get());
-}
-
 static void
 GetExtensionFromURI(nsIURI* uri, nsCString& ext)
 {
@@ -557,50 +551,6 @@ nsObjectLoadingContent::MakePluginListener()
 }
 
 
-bool
-nsObjectLoadingContent::IsSupportedDocument(const nsCString& aMimeType)
-{
-  nsCOMPtr<nsIContent> thisContent =
-    do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
-  NS_ASSERTION(thisContent, "must be a content");
-
-  nsCOMPtr<nsIWebNavigationInfo> info(
-    do_GetService(NS_WEBNAVIGATION_INFO_CONTRACTID));
-  if (!info) {
-    return false;
-  }
-
-  nsCOMPtr<nsIWebNavigation> webNav;
-  nsIDocument* currentDoc = thisContent->GetComposedDoc();
-  if (currentDoc) {
-    webNav = do_GetInterface(currentDoc->GetWindow());
-  }
-
-  uint32_t supported;
-  nsresult rv = info->IsTypeSupported(aMimeType, webNav, &supported);
-
-  if (NS_FAILED(rv)) {
-    return false;
-  }
-
-  if (supported != nsIWebNavigationInfo::UNSUPPORTED) {
-    // Don't want to support plugins as documents
-    return supported != nsIWebNavigationInfo::PLUGIN;
-  }
-
-  // Try a stream converter
-  // NOTE: We treat any type we can convert from as a supported type. If a
-  // type is not actually supported, the URI loader will detect that and
-  // return an error, and we'll fallback.
-  nsCOMPtr<nsIStreamConverterService> convServ =
-    do_GetService("@mozilla.org/streamConverters;1");
-  bool canConvert = false;
-  if (convServ) {
-    rv = convServ->CanConvert(aMimeType.get(), "*/*", &canConvert);
-  }
-  return NS_SUCCEEDED(rv) && canConvert;
-}
-
 nsresult
 nsObjectLoadingContent::BindToTree(nsIDocument* aDocument,
                                    nsIContent* aParent,
@@ -2761,43 +2711,26 @@ nsObjectLoadingContent::NotifyStateChanged(ObjectType aOldType,
 nsObjectLoadingContent::ObjectType
 nsObjectLoadingContent::GetTypeOfContent(const nsCString& aMIMEType)
 {
-  if (aMIMEType.IsEmpty()) {
-    return eType_Null;
-  }
+  nsCOMPtr<nsIContent> thisContent =
+    do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
+  NS_ASSERTION(thisContent, "must be a content");
 
+  ObjectType type = static_cast<ObjectType>(
+    nsContentUtils::HtmlObjectContentTypeForMIMEType(aMIMEType, thisContent));
+
+  // Switch the result type to eType_Null ic the capability is not present.
   uint32_t caps = GetCapabilities();
-
-  if ((caps & eSupportImages) && IsSupportedImage(aMIMEType)) {
-    return eType_Image;
+  if (!(caps & eSupportImages) && type == eType_Image) {
+    type = eType_Null;
+  }
+  if (!(caps & eSupportDocuments) && type == eType_Document) {
+    type = eType_Null;
+  }
+  if (!(caps & eSupportPlugins) && type == eType_Plugin) {
+    type = eType_Null;
   }
 
-  // Faking support of the PDF content as a document for EMBED tags
-  // when internal PDF viewer is enabled.
-  if (aMIMEType.LowerCaseEqualsLiteral("application/pdf") &&
-      nsContentUtils::IsPDFJSEnabled()) {
-    return eType_Document;
-  }
-
-  // Faking support of the SWF content as a document for EMBED tags
-  // when internal SWF player is enabled.
-  if (aMIMEType.LowerCaseEqualsLiteral("application/x-shockwave-flash") &&
-      nsContentUtils::IsSWFPlayerEnabled()) {
-    return eType_Document;
-  }
-
-  if ((caps & eSupportDocuments) && IsSupportedDocument(aMIMEType)) {
-    return eType_Document;
-  }
-
-  RefPtr<nsPluginHost> pluginHost = nsPluginHost::GetInst();
-  if ((caps & eSupportPlugins) &&
-      pluginHost &&
-      pluginHost->HavePluginForType(aMIMEType, nsPluginHost::eExcludeNone)) {
-    // ShouldPlay will handle checking for disabled plugins
-    return eType_Plugin;
-  }
-
-  return eType_Null;
+  return type;
 }
 
 nsPluginFrame*
diff --git a/dom/base/nsObjectLoadingContent.h b/dom/base/nsObjectLoadingContent.h
index e5ceb93520bb..7722ed37fc54 100644
--- a/dom/base/nsObjectLoadingContent.h
+++ b/dom/base/nsObjectLoadingContent.h
@@ -515,13 +515,6 @@ class nsObjectLoadingContent : public nsImageLoadingContent
      */
     bool CheckProcessPolicy(int16_t *aContentPolicy);
 
-    /**
-     * Checks whether the given type is a supported document type
-     *
-     * NOTE Does not take content policy or capabilities into account
-     */
-    bool IsSupportedDocument(const nsCString& aType);
-
     /**
      * Gets the plugin instance and creates a plugin stream listener, assigning
      * it to mFinalListener