--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -1,17 +1,17 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /*
  * Base class for all element classes; this provides an implementation
- * of DOM Core's nsIDOMElement, implements nsIContent, provides
+ * of DOM Core's Element, implements nsIContent, provides
  * utility methods for subclasses, and so forth.
  */
 
 #include "mozilla/dom/ElementInlines.h"
 
 #include "AnimationCommon.h"
 #include "mozilla/DebugOnly.h"
 #include "mozilla/dom/Animation.h"

--- a/dom/base/Element.h
+++ b/dom/base/Element.h
@@ -1,29 +1,28 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /*
  * Base class for all element classes; this provides an implementation
- * of DOM Core's nsIDOMElement, implements nsIContent, provides
+ * of DOM Core's Element, implements nsIContent, provides
  * utility methods for subclasses, and so forth.
  */
 
 #ifndef mozilla_dom_Element_h__
 #define mozilla_dom_Element_h__
 
 #include "mozilla/dom/FragmentOrElement.h" // for base class
 #include "nsChangeHint.h"                  // for enum
 #include "mozilla/EventStates.h"           // for member
 #include "mozilla/ServoTypes.h"
 #include "mozilla/dom/DirectionalityUtils.h"
-#include "nsIDOMElement.h"
 #include "nsILinkHandler.h"
 #include "nsINodeList.h"
 #include "nsNodeUtils.h"
 #include "nsAttrAndChildArray.h"
 #include "mozilla/FlushType.h"
 #include "nsDOMAttributeMap.h"
 #include "nsPresContext.h"
 #include "mozilla/CORSMode.h"

--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -1,18 +1,16 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /*
- * Base class for all element classes; this provides an implementation
- * of DOM Core's nsIDOMElement, implements nsIContent, provides
- * utility methods for subclasses, and so forth.
+ * Base class for all element classes and DocumentFragment.
  */
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Likely.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StaticPtr.h"
 
 #include "mozilla/dom/FragmentOrElement.h"

--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -65,18 +65,18 @@ public:
 
 private:
   ~nsNodeSupportsWeakRefTearoff() {}
 
   nsCOMPtr<nsINode> mNode;
 };
 
 /**
- * A generic base class for DOM elements, implementing many nsIContent,
- * nsIDOMNode and nsIDOMElement methods.
+ * A generic base class for DOM elements and document fragments,
+ * implementing many nsIContent, nsIDOMNode and Element methods.
  */
 namespace mozilla {
 namespace dom {
 
 class ShadowRoot;
 
 class FragmentOrElement : public nsIContent
 {

--- a/dom/base/IDTracker.cpp
+++ b/dom/base/IDTracker.cpp
@@ -8,17 +8,16 @@
 
 #include "mozilla/Encoding.h"
 #include "nsContentUtils.h"
 #include "nsIURI.h"
 #include "nsBindingManager.h"
 #include "nsEscape.h"
 #include "nsXBLPrototypeBinding.h"
 #include "nsIDOMNode.h"
-#include "nsIDOMElement.h"
 #include "nsCycleCollectionParticipant.h"
 
 namespace mozilla {
 namespace dom {
 
 void
 IDTracker::Reset(nsIContent* aFromContent, nsIURI* aURI,
                  bool aWatch, bool aReferenceImage)

--- a/dom/base/nsContentPermissionHelper.cpp
+++ b/dom/base/nsContentPermissionHelper.cpp
@@ -1,17 +1,16 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include <map>
 #include "nsCOMPtr.h"
-#include "nsIDOMElement.h"
 #include "nsIPrincipal.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/PContentPermission.h"
 #include "mozilla/dom/PermissionMessageUtils.h"
 #include "mozilla/dom/PContentPermissionRequestParent.h"

--- a/dom/base/nsContentPolicy.cpp
+++ b/dom/base/nsContentPolicy.cpp
@@ -12,17 +12,16 @@
 
 #include "nsISupports.h"
 #include "nsXPCOM.h"
 #include "nsContentPolicyUtils.h"
 #include "mozilla/dom/nsCSPService.h"
 #include "nsContentPolicy.h"
 #include "nsIURI.h"
 #include "nsIDocShell.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMWindow.h"
 #include "nsITabChild.h"
 #include "nsIContent.h"
 #include "nsIImageLoadingContent.h"
 #include "nsILoadContext.h"
 #include "nsCOMArray.h"
 #include "nsContentUtils.h"

--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -129,17 +129,16 @@
 #include "nsIContentSink.h"
 #include "nsIContentViewer.h"
 #include "nsIDocShell.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIDocument.h"
 #include "nsIDocumentEncoder.h"
 #include "nsIDOMChromeWindow.h"
 #include "nsIDOMDocument.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMWindowUtils.h"
 #include "nsIDragService.h"
 #include "nsIFormControl.h"
 #include "nsIForm.h"
 #include "nsIFragmentContentSink.h"
 #include "nsContainerFrame.h"
 #include "nsIHTMLDocument.h"

--- a/dom/base/nsCopySupport.cpp
+++ b/dom/base/nsCopySupport.cpp
@@ -27,17 +27,16 @@
 #include "nsIDocShell.h"
 #include "nsIContentViewerEdit.h"
 #include "nsIClipboardHelper.h"
 #include "nsISelectionController.h"
 
 #include "nsPIDOMWindow.h"
 #include "nsIDocument.h"
 #include "nsIDOMNode.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMDocument.h"
 #include "nsIHTMLDocument.h"
 #include "nsGkAtoms.h"
 #include "nsIFrame.h"
 #include "nsIURI.h"
 #include "nsIURIMutator.h"
 #include "nsISimpleEnumerator.h"
 

--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -108,17 +108,16 @@
 #include "nsIScriptSecurityManager.h"
 #include "nsIPermissionManager.h"
 #include "nsIPrincipal.h"
 #include "ExpandedPrincipal.h"
 #include "NullPrincipal.h"
 
 #include "nsIDOMWindow.h"
 #include "nsPIDOMWindow.h"
-#include "nsIDOMElement.h"
 #include "nsFocusManager.h"
 
 // for radio group stuff
 #include "nsIRadioVisitor.h"
 #include "nsIFormControl.h"
 
 #include "nsBidiUtils.h"
 

--- a/dom/base/nsDocumentEncoder.cpp
+++ b/dom/base/nsDocumentEncoder.cpp
@@ -15,17 +15,16 @@
 #include "nsIFactory.h"
 #include "nsISupports.h"
 #include "nsIDocument.h"
 #include "nsIHTMLDocument.h"
 #include "nsCOMPtr.h"
 #include "nsIContentSerializer.h"
 #include "mozilla/Encoding.h"
 #include "nsIOutputStream.h"
-#include "nsIDOMElement.h"
 #include "nsRange.h"
 #include "nsIDOMDocument.h"
 #include "nsGkAtoms.h"
 #include "nsIContent.h"
 #include "nsIScriptContext.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptSecurityManager.h"
 #include "mozilla/dom/Selection.h"

--- a/dom/base/nsFocusManager.cpp
+++ b/dom/base/nsFocusManager.cpp
@@ -13,17 +13,16 @@
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsGkAtoms.h"
 #include "nsGlobalWindow.h"
 #include "nsContentUtils.h"
 #include "nsDocument.h"
 #include "nsIContentParent.h"
 #include "nsPIDOMWindow.h"
 #include "nsIDOMChromeWindow.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMRange.h"
 #include "nsIHTMLDocument.h"
 #include "nsIDocShell.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIFormControl.h"
 #include "nsLayoutUtils.h"
 #include "nsIPresShell.h"

--- a/dom/base/nsFocusManager.h
+++ b/dom/base/nsFocusManager.h
@@ -59,17 +59,17 @@ public:
 
   /**
    * Retrieve the single focus manager.
    */
   static nsFocusManager* GetFocusManager() { return sInstance; }
 
   /**
    * A faster version of nsIFocusManager::GetFocusedElement, returning a
-   * raw Element pointer (instead of having AddRef-ed nsIDOMElement
+   * raw Element pointer (instead of having AddRef-ed Element
    * pointer filled in to an out-parameter).
    */
   mozilla::dom::Element* GetFocusedElement() { return mFocusedElement; }
 
   /**
    * Returns true if aContent currently has focus.
    */
   bool IsFocused(nsIContent* aContent);

--- a/dom/base/nsGlobalWindowCommands.cpp
+++ b/dom/base/nsGlobalWindowCommands.cpp
@@ -3,17 +3,16 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 
 #include "nsGlobalWindowCommands.h"
 
 #include "nsIComponentManager.h"
-#include "nsIDOMElement.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsCRT.h"
 #include "nsString.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Preferences.h"
 
 #include "nsIControllerCommandTable.h"

--- a/dom/base/nsGlobalWindowInner.cpp
+++ b/dom/base/nsGlobalWindowInner.cpp
@@ -106,17 +106,16 @@
 #include "nsIWidgetListener.h"
 #include "nsIBaseWindow.h"
 #include "nsIDeviceSensors.h"
 #include "nsIContent.h"
 #include "nsIDocShell.h"
 #include "nsIDocument.h"
 #include "Crypto.h"
 #include "nsIDOMDocument.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMOfflineResourceList.h"
 #include "nsDOMString.h"
 #include "nsIEmbeddingSiteWindow.h"
 #include "nsThreadUtils.h"
 #include "nsILoadContext.h"
 #include "nsIPresShell.h"
 #include "nsIScrollableFrame.h"
 #include "nsView.h"
@@ -4969,38 +4968,16 @@ nsGlobalWindowInner::GetComputedStyle(El
 already_AddRefed<nsICSSDeclaration>
 nsGlobalWindowInner::GetDefaultComputedStyle(Element& aElt,
                                              const nsAString& aPseudoElt,
                                              ErrorResult& aError)
 {
   return GetComputedStyleHelper(aElt, aPseudoElt, true, aError);
 }
 
-nsresult
-nsGlobalWindowInner::GetComputedStyleHelper(nsIDOMElement* aElt,
-                                            const nsAString& aPseudoElt,
-                                            bool aDefaultStylesOnly,
-                                            nsICSSDeclaration** aReturn)
-{
-  NS_ENSURE_ARG_POINTER(aReturn);
-  *aReturn = nullptr;
-
-  nsCOMPtr<dom::Element> element = do_QueryInterface(aElt);
-  if (!element) {
-    return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
-  }
-
-  ErrorResult rv;
-  nsCOMPtr<nsICSSDeclaration> cs =
-    GetComputedStyleHelper(*element, aPseudoElt, aDefaultStylesOnly, rv);
-  cs.forget(aReturn);
-
-  return rv.StealNSResult();
-}
-
 already_AddRefed<nsICSSDeclaration>
 nsGlobalWindowInner::GetComputedStyleHelper(Element& aElt,
                                             const nsAString& aPseudoElt,
                                             bool aDefaultStylesOnly,
                                             ErrorResult& aError)
 {
   FORWARD_TO_OUTER_OR_THROW(GetComputedStyleHelperOuter,
                             (aElt, aPseudoElt, aDefaultStylesOnly),

--- a/dom/base/nsGlobalWindowInner.h
+++ b/dom/base/nsGlobalWindowInner.h
@@ -1236,20 +1236,16 @@ protected:
                     mozilla::ErrorResult& aRv);
 
 protected:
   already_AddRefed<nsICSSDeclaration>
     GetComputedStyleHelper(mozilla::dom::Element& aElt,
                            const nsAString& aPseudoElt,
                            bool aDefaultStylesOnly,
                            mozilla::ErrorResult& aError);
-  nsresult GetComputedStyleHelper(nsIDOMElement* aElt,
-                                  const nsAString& aPseudoElt,
-                                  bool aDefaultStylesOnly,
-                                  nsICSSDeclaration** aReturn);
 
   nsGlobalWindowInner* InnerForSetTimeoutOrInterval(mozilla::ErrorResult& aError);
 
   void PostMessageMoz(JSContext* aCx, JS::Handle<JS::Value> aMessage,
                       const nsAString& aTargetOrigin,
                       JS::Handle<JS::Value> aTransfer,
                       nsIPrincipal& aSubjectPrincipal,
                       mozilla::ErrorResult& aError);

--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -103,17 +103,16 @@
 #include "nsIWidgetListener.h"
 #include "nsIBaseWindow.h"
 #include "nsIDeviceSensors.h"
 #include "nsIContent.h"
 #include "nsIDocShell.h"
 #include "nsIDocument.h"
 #include "Crypto.h"
 #include "nsIDOMDocument.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMOfflineResourceList.h"
 #include "nsDOMString.h"
 #include "nsIEmbeddingSiteWindow.h"
 #include "nsThreadUtils.h"
 #include "nsILoadContext.h"
 #include "nsIPresShell.h"
 #include "nsIScrollableFrame.h"
 #include "nsView.h"

--- a/dom/base/nsHTMLContentSerializer.cpp
+++ b/dom/base/nsHTMLContentSerializer.cpp
@@ -7,17 +7,16 @@
 /*
  * nsIContentSerializer implementation that can be used with an
  * nsIDocumentEncoder to convert an HTML (not XHTML!) DOM to an HTML
  * string that could be parsed into more or less the original DOM.
  */
 
 #include "nsHTMLContentSerializer.h"
 
-#include "nsIDOMElement.h"
 #include "nsIContent.h"
 #include "nsIDocument.h"
 #include "nsElementTable.h"
 #include "nsNameSpaceManager.h"
 #include "nsString.h"
 #include "nsUnicharUtils.h"
 #include "nsIServiceManager.h"
 #include "nsIDocumentEncoder.h"

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -89,17 +89,16 @@ class nsIBFCacheEntry;
 class nsIChannel;
 class nsIContent;
 class nsIContentSink;
 class nsIDocShell;
 class nsIDocShellTreeItem;
 class nsIDocumentEncoder;
 class nsIDocumentObserver;
 class nsIDOMDocument;
-class nsIDOMElement;
 class nsIHTMLCollection;
 class nsILayoutHistoryState;
 class nsILoadContext;
 class nsIObjectLoadingContent;
 class nsIObserver;
 class nsIPrincipal;
 class nsIRequest;
 class nsIRunnable;

--- a/dom/base/nsINode.h
+++ b/dom/base/nsINode.h
@@ -37,17 +37,16 @@
 #endif
 
 class nsAttrAndChildArray;
 class nsAttrChildContentList;
 class nsDOMAttributeMap;
 class nsIAnimationObserver;
 class nsIContent;
 class nsIDocument;
-class nsIDOMElement;
 class nsIFrame;
 class nsIMutationObserver;
 class nsINode;
 class nsINodeList;
 class nsIPresShell;
 class nsIPrincipal;
 class nsIURI;
 class nsNodeSupportsWeakRefTearoff;

--- a/dom/base/nsInProcessTabChildGlobal.h
+++ b/dom/base/nsInProcessTabChildGlobal.h
@@ -12,17 +12,16 @@
 #include "mozilla/dom/ContentFrameMessageManager.h"
 #include "nsCOMPtr.h"
 #include "nsFrameMessageManager.h"
 #include "nsIScriptContext.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsIScriptContext.h"
 #include "nsIClassInfo.h"
 #include "nsIDocShell.h"
-#include "nsIDOMElement.h"
 #include "nsCOMArray.h"
 #include "nsIRunnable.h"
 #include "nsIGlobalObject.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsWeakReference.h"
 
 namespace mozilla {
 class EventChainPreVisitor;

--- a/dom/base/nsXHTMLContentSerializer.cpp
+++ b/dom/base/nsXHTMLContentSerializer.cpp
@@ -7,17 +7,16 @@
 /*
  * nsIContentSerializer implementation that can be used with an
  * nsIDocumentEncoder to convert an XHTML (not HTML!) DOM to an XHTML
  * string that could be parsed into more or less the original DOM.
  */
 
 #include "nsXHTMLContentSerializer.h"
 
-#include "nsIDOMElement.h"
 #include "nsIContent.h"
 #include "nsIDocument.h"
 #include "nsElementTable.h"
 #include "nsNameSpaceManager.h"
 #include "nsString.h"
 #include "nsUnicharUtils.h"
 #include "nsIServiceManager.h"
 #include "nsIDocumentEncoder.h"

--- a/dom/base/test/unit/test_xml_serializer.js
+++ b/dom/base/test/unit/test_xml_serializer.js
@@ -129,18 +129,17 @@ function test4() {
   Assert.equal(SerializeXML(doc),
                  '<root xmlns="ns1" a0:local="val" xmlns:a0="ns1"/>');
 
   // Tree-walking test
   doc = ParseXML('<root xmlns="ns1" xmlns:a="ns2">'+
                  '<child xmlns:b="ns2" xmlns:a="ns3">'+
                  '<child2/></child></root>');
   root = doc.documentElement;
-  // Have to QI here -- no classinfo flattening in xpcshell, apparently
-  var node = root.firstChild.firstChild.QueryInterface(nsIDOMElement);
+  var node = root.firstChild.firstChild;
   node.setAttributeNS("ns4", "l1", "v1");
   node.setAttributeNS("ns4", "p2:l2", "v2");
   node.setAttributeNS("", "l3", "v3");
   node.setAttributeNS("ns3", "l4", "v4");
   node.setAttributeNS("ns3", "p5:l5", "v5");
   node.setAttributeNS("ns3", "a:l6", "v6");
   node.setAttributeNS("ns2", "l7", "v7");
   node.setAttributeNS("ns2", "p8:l8", "v8");
@@ -246,33 +245,31 @@ function test7() {
                       "http://www.w3.org/1999/xhtml");
   do_check_serialize(doc);
   Assert.equal(SerializeXML(doc), '<root><child1/></root>');
 
   doc = ParseXML('<root xmlns="http://www.w3.org/1999/xhtml">' +
                  '<child1 xmlns=""><child2/></child1></root>')
   root = doc.documentElement;
 
-  // No interface flattening in xpcshell
-  var child1 = root.firstChild.QueryInterface(nsIDOMElement);
+  var child1 = root.firstChild;
   child1.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns",
                         "http://www.w3.org/1999/xhtml");
   do_check_serialize(doc);
   Assert.equal(SerializeXML(doc),
                '<root xmlns="http://www.w3.org/1999/xhtml"><child1 xmlns="">' +
                '<child2/></child1></root>');
 
   doc = ParseXML('<root xmlns="http://www.w3.org/1999/xhtml">' +
                  '<child1 xmlns="">' +
                  '<child2 xmlns="http://www.w3.org/1999/xhtml"></child2>' +
                  '</child1></root>')
   root = doc.documentElement;
-  // No interface flattening in xpcshell
-  child1 = root.firstChild.QueryInterface(nsIDOMElement);
-  var child2 = child1.firstChild.QueryInterface(nsIDOMElement);
+  child1 = root.firstChild;
+  var child2 = child1.firstChild;
   child1.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns",
                         "http://www.w3.org/1999/xhtml");
   child2.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns", "");
   do_check_serialize(doc);
   Assert.equal(SerializeXML(doc),
                '<root xmlns="http://www.w3.org/1999/xhtml"><child1 xmlns="">' +
                '<a0:child2 xmlns:a0="http://www.w3.org/1999/xhtml" xmlns=""></a0:child2></child1></root>');
 }

--- a/dom/events/DataTransfer.h
+++ b/dom/events/DataTransfer.h
@@ -6,17 +6,16 @@
 
 #ifndef mozilla_dom_DataTransfer_h
 #define mozilla_dom_DataTransfer_h
 
 #include "nsString.h"
 #include "nsTArray.h"
 #include "nsIVariant.h"
 #include "nsIPrincipal.h"
-#include "nsIDOMElement.h"
 #include "nsIDragService.h"
 #include "nsCycleCollectionParticipant.h"
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/dom/BindingDeclarations.h"

--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -3348,23 +3348,20 @@ EventStateManager::PostHandleEvent(nsPre
         }
 
         // The rest is left button-specific.
         if (mouseEvent->button != WidgetMouseEvent::eLeftButton) {
           break;
         }
 
         if (activeContent) {
-          // The nearest enclosing element goes into the
-          // :active state.  If we fail the QI to DOMElement,
-          // then we know we're only a node, and that we need
-          // to obtain our parent element and put it into :active
-          // instead.
-          nsCOMPtr<nsIDOMElement> elt(do_QueryInterface(activeContent));
-          if (!elt) {
+          // The nearest enclosing element goes into the :active state.  If
+          // we're not an element (so we're text or something) we need to obtain
+          // our parent element and put it into :active instead.
+          if (!activeContent->IsElement()) {
             nsIContent* par = activeContent->GetParent();
             if (par)
               activeContent = par;
           }
         }
       }
       else {
         // if we're here, the event handler returned false, so stop

--- a/dom/html/ImageDocument.cpp
+++ b/dom/html/ImageDocument.cpp
@@ -26,17 +26,16 @@
 #include "imgIContainer.h"
 #include "imgINotificationObserver.h"
 #include "nsIPresShell.h"
 #include "nsPresContext.h"
 #include "nsIChannel.h"
 #include "nsIContentPolicy.h"
 #include "nsContentPolicyUtils.h"
 #include "nsPIDOMWindow.h"
-#include "nsIDOMElement.h"
 #include "nsError.h"
 #include "nsURILoader.h"
 #include "nsIDocShell.h"
 #include "nsIContentViewer.h"
 #include "nsThreadUtils.h"
 #include "nsIScrollableFrame.h"
 #include "nsContentUtils.h"
 #include "mozilla/Preferences.h"

--- a/dom/html/nsBrowserElement.cpp
+++ b/dom/html/nsBrowserElement.cpp
@@ -10,17 +10,16 @@
 #include "mozilla/Services.h"
 #include "mozilla/dom/BrowserElementBinding.h"
 #include "mozilla/dom/DOMRequest.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/dom/ToJSValue.h"
 
 #include "nsComponentManagerUtils.h"
 #include "nsFrameLoader.h"
-#include "nsIDOMElement.h"
 #include "nsIMozBrowserFrame.h"
 #include "nsINode.h"
 #include "nsIPrincipal.h"
 
 using namespace mozilla::dom;
 
 namespace mozilla {
 

--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -18,17 +18,16 @@
 #include "nsIHTMLContentSink.h"
 #include "nsIXMLContentSink.h"
 #include "nsHTMLParts.h"
 #include "nsHTMLStyleSheet.h"
 #include "nsGkAtoms.h"
 #include "nsIPresShell.h"
 #include "nsPresContext.h"
 #include "nsIDOMNode.h" // for Find
-#include "nsIDOMElement.h"
 #include "nsPIDOMWindow.h"
 #include "nsDOMString.h"
 #include "nsIStreamListener.h"
 #include "nsIURI.h"
 #include "nsIURIMutator.h"
 #include "nsIIOService.h"
 #include "nsNetUtil.h"
 #include "nsIPrivateBrowsingChannel.h"

--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -49,17 +49,16 @@
 #include "nsFocusManager.h"
 #include "nsFrameLoader.h"
 #include "nsFrameManager.h"
 #include "nsIBaseWindow.h"
 #include "nsIBrowser.h"
 #include "nsIContent.h"
 #include "nsIDocShell.h"
 #include "nsIDocShellTreeOwner.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMWindow.h"
 #include "nsIDOMWindowUtils.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsILoadInfo.h"
 #include "nsIPromptFactory.h"
 #include "nsIURI.h"
 #include "nsIWindowWatcher.h"
 #include "nsIWebBrowserChrome.h"

--- a/dom/plugins/base/nsJSNPRuntime.cpp
+++ b/dom/plugins/base/nsJSNPRuntime.cpp
@@ -16,17 +16,16 @@
 #include "nsIGlobalObject.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptContext.h"
 #include "nsDOMJSUtils.h"
 #include "nsJSUtils.h"
 #include "nsIDocument.h"
 #include "nsIXPConnect.h"
 #include "xpcpublic.h"
-#include "nsIDOMElement.h"
 #include "nsIContent.h"
 #include "nsPluginInstanceOwner.h"
 #include "nsWrapperCacheInlines.h"
 #include "js/GCHashTable.h"
 #include "js/TracingAPI.h"
 #include "js/Wrapper.h"
 #include "mozilla/HashFunctions.h"
 #include "mozilla/dom/ScriptSettings.h"

--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -21,29 +21,30 @@
 #include "nsIServiceManager.h"
 #include "nsThreadUtils.h"
 #include "mozilla/Preferences.h"
 #include "nsPluginInstanceOwner.h"
 
 #include "nsPluginsDir.h"
 #include "nsPluginLogging.h"
 
-#include "nsIDOMElement.h"
 #include "nsPIDOMWindow.h"
 #include "nsGlobalWindow.h"
 #include "nsIDocument.h"
 #include "nsIContent.h"
 #include "nsIIDNService.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptContext.h"
 #include "nsDOMJSUtils.h"
 #include "nsIPrincipal.h"
 #include "nsWildCard.h"
 #include "nsContentUtils.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/ToJSValue.h"
 #include "nsIXULRuntime.h"
 #include "nsIXPConnect.h"
 
 #include "nsIObserverService.h"
 #include <prinrval.h>
 
 #ifdef MOZ_WIDGET_COCOA
 #include <Carbon/Carbon.h>
@@ -708,17 +709,17 @@ NPObject*
     NPN_PLUGIN_LOG(PLUGIN_LOG_ALWAYS,("NPN_getpluginelement called from the wrong thread\n"));
     return nullptr;
   }
 
   nsNPAPIPluginInstance* inst = static_cast<nsNPAPIPluginInstance*>(npp->ndata);
   if (!inst)
     return nullptr;
 
-  nsCOMPtr<nsIDOMElement> element;
+  RefPtr<dom::Element> element;
   inst->GetDOMElement(getter_AddRefs(element));
 
   if (!element)
     return nullptr;
 
   nsIDocument *doc = GetDocumentFromNPP(npp);
   if (NS_WARN_IF(!doc)) {
     return nullptr;
@@ -728,20 +729,26 @@ NPObject*
   if (NS_WARN_IF(!jsapi.Init(doc->GetInnerWindow()))) {
     return nullptr;
   }
   JSContext* cx = jsapi.cx();
 
   nsCOMPtr<nsIXPConnect> xpc(do_GetService(nsIXPConnect::GetCID()));
   NS_ENSURE_TRUE(xpc, nullptr);
 
-  JS::RootedObject obj(cx);
-  xpc->WrapNative(cx, ::JS::CurrentGlobalOrNull(cx), element,
-                  NS_GET_IID(nsIDOMElement), obj.address());
-  NS_ENSURE_TRUE(obj, nullptr);
+  JS::RootedValue val(cx);
+  if (!ToJSValue(cx, element, &val)) {
+    return nullptr;
+  }
+
+  if (NS_WARN_IF(!val.isObject())) {
+    return nullptr;
+  }
+
+  JS::RootedObject obj(cx, &val.toObject());
 
   return nsJSObjWrapper::GetNewOrUsed(npp, obj);
 }
 
 NPIdentifier
 _getstringidentifier(const NPUTF8* name)
 {
   if (!name) {
@@ -1446,28 +1453,23 @@ NPError
   }
 
   case NPNVdocumentOrigin: {
     nsNPAPIPluginInstance *inst = (nsNPAPIPluginInstance *)npp->ndata;
     if (!inst) {
       return NPERR_GENERIC_ERROR;
     }
 
-    nsCOMPtr<nsIDOMElement> element;
+    RefPtr<dom::Element> element;
     inst->GetDOMElement(getter_AddRefs(element));
     if (!element) {
       return NPERR_GENERIC_ERROR;
     }
 
-    nsCOMPtr<nsIContent> content(do_QueryInterface(element));
-    if (!content) {
-      return NPERR_GENERIC_ERROR;
-    }
-
-    nsIPrincipal* principal = content->NodePrincipal();
+    nsIPrincipal* principal = element->NodePrincipal();
 
     nsAutoString utf16Origin;
     res = nsContentUtils::GetUTFOrigin(principal, utf16Origin);
     if (NS_FAILED(res)) {
       return NPERR_GENERIC_ERROR;
     }
 
     nsCOMPtr<nsIIDNService> idnService = do_GetService(NS_IDNSERVICE_CONTRACTID);

--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -13,31 +13,31 @@
 #include "nsNPAPIPlugin.h"
 #include "nsNPAPIPluginStreamListener.h"
 #include "nsPluginHost.h"
 #include "nsPluginLogging.h"
 #include "nsContentUtils.h"
 #include "nsPluginInstanceOwner.h"
 
 #include "nsThreadUtils.h"
-#include "nsIDOMElement.h"
 #include "nsIDocument.h"
 #include "nsIDocShell.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptContext.h"
 #include "nsDirectoryServiceDefs.h"
 #include "nsJSNPRuntime.h"
 #include "nsPluginStreamListenerPeer.h"
 #include "nsSize.h"
 #include "nsNetCID.h"
 #include "nsIContent.h"
 #include "nsVersionComparator.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Unused.h"
 #include "nsILoadContext.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/HTMLObjectElementBinding.h"
 #include "AudioChannelService.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
 
 using namespace mozilla;
 using namespace mozilla::plugins::parent;
@@ -1083,17 +1083,17 @@ nsNPAPIPluginInstance::ConvertPoint(doub
   if (mOwner) {
     return mOwner->ConvertPoint(sourceX, sourceY, sourceSpace, destX, destY, destSpace);
   }
 
   return false;
 }
 
 nsresult
-nsNPAPIPluginInstance::GetDOMElement(nsIDOMElement* *result)
+nsNPAPIPluginInstance::GetDOMElement(Element** result)
 {
   if (!mOwner) {
     *result = nullptr;
     return NS_ERROR_FAILURE;
   }
 
   return mOwner->GetDOMElement(result);
 }

--- a/dom/plugins/base/nsNPAPIPluginInstance.h
+++ b/dom/plugins/base/nsNPAPIPluginInstance.h
@@ -26,16 +26,22 @@
 #include "mozilla/WeakPtr.h"
 
 class nsPluginStreamListenerPeer; // browser-initiated stream class
 class nsNPAPIPluginStreamListener; // plugin-initiated stream class
 class nsIPluginInstanceOwner;
 class nsIOutputStream;
 class nsPluginInstanceOwner;
 
+namespace mozilla {
+namespace dom {
+class Element;
+} // namespace dom
+} // namespace mozilla
+
 #if defined(OS_WIN)
 const NPDrawingModel kDefaultDrawingModel = NPDrawingModelSyncWin;
 #elif defined(MOZ_X11)
 const NPDrawingModel kDefaultDrawingModel = NPDrawingModelSyncX;
 #elif defined(XP_MACOSX)
 #ifndef NP_NO_QUICKDRAW
 const NPDrawingModel kDefaultDrawingModel = NPDrawingModelQuickDraw; // Not supported
 #else
@@ -185,17 +191,17 @@ public:
   void SetCached(bool aCache);
 
   already_AddRefed<nsPIDOMWindowOuter> GetDOMWindow();
 
   nsresult PrivateModeStateChanged(bool aEnabled);
 
   nsresult IsPrivateBrowsing(bool *aEnabled);
 
-  nsresult GetDOMElement(nsIDOMElement* *result);
+  nsresult GetDOMElement(mozilla::dom::Element* *result);
 
   nsNPAPITimer* TimerWithID(uint32_t id, uint32_t* index);
   uint32_t      ScheduleTimer(uint32_t interval, NPBool repeat, void (*timerFunc)(NPP npp, uint32_t timerID));
   void          UnscheduleTimer(uint32_t timerID);
   NPBool        ConvertPoint(double sourceX, double sourceY, NPCoordinateSpace sourceSpace, double *destX, double *destY, NPCoordinateSpace destSpace);
 
 
   nsTArray<nsNPAPIPluginStreamListener*> *StreamListeners();

--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -47,16 +47,17 @@
 #include "nsIBlocklistService.h"
 #include "nsVersionComparator.h"
 #include "nsIObjectLoadingContent.h"
 #include "nsIWritablePropertyBag2.h"
 #include "nsICategoryManager.h"
 #include "nsPluginStreamListenerPeer.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/FakePluginTagInitBinding.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/LoadInfo.h"
 #include "mozilla/plugins/PluginBridge.h"
 #include "mozilla/plugins/PluginTypes.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ipc/URIUtils.h"
 
@@ -65,17 +66,16 @@
 #include "nsXPCOMCID.h"
 #include "nsISupportsPrimitives.h"
 
 #include "nsXULAppAPI.h"
 #include "nsIXULRuntime.h"
 
 // for the dialog
 #include "nsIWindowWatcher.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMWindow.h"
 
 #include "nsNetCID.h"
 #include "mozilla/Sprintf.h"
 #include "nsThreadUtils.h"
 #include "nsIInputStreamTee.h"
 #include "nsQueryObject.h"
 
@@ -3292,34 +3292,33 @@ nsresult nsPluginHost::NewPluginURLStrea
   NS_ENSURE_SUCCESS(rv, rv);
 
   RefPtr<nsPluginStreamListenerPeer> listenerPeer = new nsPluginStreamListenerPeer();
   NS_ENSURE_TRUE(listenerPeer, NS_ERROR_OUT_OF_MEMORY);
 
   rv = listenerPeer->Initialize(url, aInstance, aListener);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  nsCOMPtr<nsIDOMElement> element;
+  RefPtr<dom::Element> element;
   nsCOMPtr<nsIDocument> doc;
   if (owner) {
     owner->GetDOMElement(getter_AddRefs(element));
     owner->GetDocument(getter_AddRefs(doc));
   }
 
-  nsCOMPtr<nsINode> requestingNode(do_QueryInterface(element));
-  NS_ENSURE_TRUE(requestingNode, NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE(element, NS_ERROR_FAILURE);
 
   nsCOMPtr<nsIChannel> channel;
   // @arg loadgroup:
   // do not add this internal plugin's channel on the
   // load group otherwise this channel could be canceled
   // form |nsDocShell::OnLinkClickSync| bug 166613
   rv = NS_NewChannel(getter_AddRefs(channel),
                      url,
-                     requestingNode,
+                     element,
                      nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_INHERITS |
                      nsILoadInfo::SEC_FORCE_INHERIT_PRINCIPAL,
                      nsIContentPolicy::TYPE_OBJECT_SUBREQUEST,
                      nullptr, // aPerformanceStorage
                      nullptr,  // aLoadGroup
                      listenerPeer,
                      nsIRequest::LOAD_NORMAL | nsIChannel::LOAD_CLASSIFY_URI |
                      nsIChannel::LOAD_BYPASS_SERVICE_WORKER);
@@ -3852,17 +3851,17 @@ nsPluginHost::PluginCrashed(nsNPAPIPlugi
 
   // Invalidate each nsPluginInstanceTag for the crashed plugin
 
   for (uint32_t i = mInstances.Length(); i > 0; i--) {
     nsNPAPIPluginInstance* instance = mInstances[i - 1];
     if (instance->GetPlugin() == aPlugin) {
       // notify the content node (nsIObjectLoadingContent) that the
       // plugin has crashed
-      nsCOMPtr<nsIDOMElement> domElement;
+      RefPtr<dom::Element> domElement;
       instance->GetDOMElement(getter_AddRefs(domElement));
       nsCOMPtr<nsIObjectLoadingContent> objectContent(do_QueryInterface(domElement));
       if (objectContent) {
         objectContent->PluginCrashed(crashedPluginTag, pluginDumpID, browserDumpID,
                                      submittedCrashReport);
       }
 
       instance->Destroy();
@@ -3947,17 +3946,17 @@ nsPluginHost::DestroyRunningInstances(ns
     if (instance->IsRunning() && (!aPluginTag || aPluginTag == TagForPlugin(instance->GetPlugin()))) {
       instance->SetWindow(nullptr);
       instance->Stop();
 
       // Get rid of all the instances without the possibility of caching.
       nsPluginTag* pluginTag = TagForPlugin(instance->GetPlugin());
       instance->SetWindow(nullptr);
 
-      nsCOMPtr<nsIDOMElement> domElement;
+      RefPtr<dom::Element> domElement;
       instance->GetDOMElement(getter_AddRefs(domElement));
       nsCOMPtr<nsIObjectLoadingContent> objectContent =
         do_QueryInterface(domElement);
 
       instance->Destroy();
 
       mInstances.RemoveElement(instance);
       OnPluginInstanceDestroyed(pluginTag);

--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -47,16 +47,17 @@ using mozilla::DefaultXDisplay;
 #include "ImageContainer.h"
 #include "GLContext.h"
 #include "EGLUtils.h"
 #include "nsIContentInlines.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/TextEvents.h"
 #include "mozilla/dom/DragEvent.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/HTMLObjectElementBinding.h"
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/dom/WheelEventBinding.h"
 #include "nsFrameSelection.h"
 #include "PuppetWidget.h"
 #include "nsPIWindowRoot.h"
 #include "mozilla/IMEStateManager.h"
@@ -382,17 +383,17 @@ void nsPluginInstanceOwner::GetAttribute
 {
   nsCOMPtr<nsIObjectLoadingContent> content = do_QueryReferent(mContent);
   nsObjectLoadingContent *loadingContent =
     static_cast<nsObjectLoadingContent*>(content.get());
 
   loadingContent->GetPluginAttributes(attributes);
 }
 
-NS_IMETHODIMP nsPluginInstanceOwner::GetDOMElement(nsIDOMElement* *result)
+NS_IMETHODIMP nsPluginInstanceOwner::GetDOMElement(Element** result)
 {
   return CallQueryReferent(mContent.get(), result);
 }
 
 nsresult nsPluginInstanceOwner::GetInstance(nsNPAPIPluginInstance **aInstance)
 {
   NS_ENSURE_ARG_POINTER(aInstance);
 

--- a/dom/plugins/base/nsPluginInstanceOwner.h
+++ b/dom/plugins/base/nsPluginInstanceOwner.h
@@ -32,16 +32,17 @@ class nsDisplayListBuilder;
 
 #if defined(MOZ_X11)
 class gfxContext;
 #endif
 
 namespace mozilla {
 class TextComposition;
 namespace dom {
+class Element;
 class Event;
 struct MozPluginParameter;
 } // namespace dom
 namespace widget {
 class PuppetWidget;
 } // namespace widget
 } // namespace mozilla
 
@@ -90,17 +91,17 @@ public:
 
   /**
    * Returns the DOM element corresponding to the tag which references
    * this plugin in the document.
    *
    * @param aDOMElement - resulting DOM element
    * @result - NS_OK if this operation was successful
    */
-  NS_IMETHOD GetDOMElement(nsIDOMElement* * aResult);
+  NS_IMETHOD GetDOMElement(mozilla::dom::Element** aResult);
 
   // nsIDOMEventListener interfaces
   NS_DECL_NSIDOMEVENTLISTENER
 
   nsresult ProcessMouseDown(mozilla::dom::Event* aMouseEvent);
   nsresult ProcessKeyPress(mozilla::dom::Event* aKeyEvent);
   nsresult Destroy();
 

--- a/dom/plugins/base/nsPluginStreamListenerPeer.cpp
+++ b/dom/plugins/base/nsPluginStreamListenerPeer.cpp
@@ -1,17 +1,16 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsPluginStreamListenerPeer.h"
 #include "nsIContentPolicy.h"
 #include "nsContentPolicyUtils.h"
-#include "nsIDOMElement.h"
 #include "nsIStreamConverterService.h"
 #include "nsIStreamLoader.h"
 #include "nsIHttpChannel.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsIFileChannel.h"
 #include "nsMimeTypes.h"
 #include "nsISupportsPrimitives.h"
 #include "nsNetCID.h"

--- a/dom/plugins/ipc/PluginInstanceParent.cpp
+++ b/dom/plugins/ipc/PluginInstanceParent.cpp
@@ -21,17 +21,16 @@
 #include "gfxASurface.h"
 #include "gfxContext.h"
 #include "gfxPlatform.h"
 #include "gfxSharedImageSurface.h"
 #include "nsNetUtil.h"
 #include "nsNPAPIPluginInstance.h"
 #include "nsPluginInstanceOwner.h"
 #include "nsFocusManager.h"
-#include "nsIDOMElement.h"
 #ifdef MOZ_X11
 #include "gfxXlibSurface.h"
 #endif
 #include "gfxUtils.h"
 #include "mozilla/gfx/2D.h"
 #include "Layers.h"
 #include "ImageContainer.h"
 #include "GLContext.h"
@@ -2217,21 +2216,20 @@ PluginInstanceParent::AnswerPluginFocusC
     // when it's plugin window (or one of it's children) receives keyboard
     // focus. We detect this and forward a notification here so we can update
     // focus.
 #if defined(OS_WIN)
     if (gotFocus) {
       nsPluginInstanceOwner* owner = GetOwner();
       if (owner) {
         nsIFocusManager* fm = nsFocusManager::GetFocusManager();
-        nsCOMPtr<nsIDOMElement> element;
+        RefPtr<dom::Element> element;
         owner->GetDOMElement(getter_AddRefs(element));
         if (fm && element) {
-          nsCOMPtr<dom::Element> domElement(do_QueryInterface(element));
-          fm->SetFocus(domElement, 0);
+          fm->SetFocus(element, 0);
         }
       }
     }
     return IPC_OK();
 #else
     NS_NOTREACHED("PluginInstanceParent::AnswerPluginFocusChange not implemented!");
     return IPC_FAIL_NO_REASON(this);
 #endif

--- a/dom/plugins/ipc/PluginModuleParent.cpp
+++ b/dom/plugins/ipc/PluginModuleParent.cpp
@@ -8,16 +8,17 @@
 
 #include "base/process_util.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/ipc/CrashReporterClient.h"
 #include "mozilla/ipc/CrashReporterHost.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
 #include "mozilla/ipc/MessageChannel.h"
 #include "mozilla/ipc/ProtocolUtils.h"
 #include "mozilla/plugins/BrowserStreamParent.h"
 #include "mozilla/plugins/PluginBridge.h"
 #include "mozilla/plugins/PluginInstanceParent.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ProcessHangMonitor.h"
@@ -2467,20 +2468,20 @@ PluginModuleParent::NPP_NewInternal(NPMI
 #endif
     }
 
     instance->pdata = parentInstance;
 
     // Any IPC messages for the PluginInstance actor should be dispatched to the
     // DocGroup for the plugin's document.
     RefPtr<nsPluginInstanceOwner> owner = parentInstance->GetOwner();
-    nsCOMPtr<nsIDOMElement> elt;
+    RefPtr<dom::Element> elt;
     owner->GetDOMElement(getter_AddRefs(elt));
-    if (nsCOMPtr<nsINode> node = do_QueryInterface(elt)) {
-        nsCOMPtr<nsIDocument> doc = node->OwnerDoc();
+    if (elt) {
+        nsCOMPtr<nsIDocument> doc = elt->OwnerDoc();
         if (doc) {
             nsCOMPtr<nsIEventTarget> eventTarget = doc->EventTargetFor(TaskCategory::Other);
             SetEventTargetForActor(parentInstance, eventTarget);
         }
     }
 
     if (!SendPPluginInstanceConstructor(parentInstance,
                                         nsDependentCString(pluginType),

--- a/dom/smil/nsSMILTimedElement.cpp
+++ b/dom/smil/nsSMILTimedElement.cpp
@@ -312,17 +312,17 @@ dom::Element*
 nsSMILTimedElement::GetTargetElement()
 {
   return mAnimationElement ?
       mAnimationElement->GetTargetElementContent() :
       nullptr;
 }
 
 //----------------------------------------------------------------------
-// nsIDOMElementTimeControl methods
+// ElementTimeControl methods
 //
 // The definition of the ElementTimeControl interface differs between SMIL
 // Animation and SVG 1.1. In SMIL Animation all methods have a void return
 // type and the new instance time is simply added to the list and restart
 // semantics are applied as with any other instance time. In the SVG definition
 // the methods return a bool depending on the restart mode.
 //
 // This inconsistency has now been addressed by an erratum in SVG 1.1:

--- a/dom/smil/nsSMILTimedElement.h
+++ b/dom/smil/nsSMILTimedElement.h
@@ -58,17 +58,17 @@ public:
 
   /*
    * Returns the element targeted by the animation element. Needed for
    * registering event listeners against the appropriate element.
    */
   mozilla::dom::Element* GetTargetElement();
 
   /**
-   * Methods for supporting the nsIDOMElementTimeControl interface.
+   * Methods for supporting the ElementTimeControl interface.
    */
 
   /*
    * Adds a new begin instance time at the current container time plus or minus
    * the specified offset.
    *
    * @param aOffsetSeconds A real number specifying the number of seconds to add
    *                       to the current container time.

--- a/dom/tests/mochitest/general/test_domWindowUtils.html
+++ b/dom/tests/mochitest/general/test_domWindowUtils.html
@@ -27,20 +27,20 @@
 <script type="application/javascript">
 
 SimpleTest.waitForExplicitFinish();
 
 var domWindowUtils = SpecialPowers.getDOMWindowUtils(window);
 
 var gTests = [
 /*
-  nsIDOMElement elementFromPoint(in long aX,
-                                 in long aY,
-                                 in boolean aIgnoreRootScrollFrame,
-                                 in boolean aFlushLayout);
+  Element elementFromPoint(in long aX,
+                           in long aY,
+                           in boolean aIgnoreRootScrollFrame,
+                           in boolean aFlushLayout);
 */
 async function testElementFromPoint() {
   let onscreen = document.getElementById("onscreen");
   let offscreen = document.getElementById("offscreen");
   let htmldoc = document.documentElement;
   ok(onscreen, "on screen element exists");
   ok(offscreen, "off screen element exists");
   ok(htmldoc, "htmldoc element exists");

--- a/dom/xbl/nsBindingManager.cpp
+++ b/dom/xbl/nsBindingManager.cpp
@@ -12,17 +12,16 @@
 #include "nsIInputStream.h"
 #include "nsIURI.h"
 #include "nsIURL.h"
 #include "nsIChannel.h"
 #include "nsString.h"
 #include "plstr.h"
 #include "nsIContent.h"
 #include "nsIContentInlines.h"
-#include "nsIDOMElement.h"
 #include "nsIDocument.h"
 #include "nsContentUtils.h"
 #include "nsIPresShell.h"
 #include "nsIPresShellInlines.h"
 #include "nsIXMLContentSink.h"
 #include "nsContentCID.h"
 #include "mozilla/dom/XMLDocument.h"
 #include "nsIStreamListener.h"

--- a/dom/xbl/nsXBLService.cpp
+++ b/dom/xbl/nsXBLService.cpp
@@ -9,17 +9,16 @@
 
 #include "nsCOMPtr.h"
 #include "nsNetUtil.h"
 #include "nsXBLService.h"
 #include "nsXBLWindowKeyHandler.h"
 #include "nsIInputStream.h"
 #include "nsNameSpaceManager.h"
 #include "nsIURI.h"
-#include "nsIDOMElement.h"
 #include "nsIURL.h"
 #include "nsIChannel.h"
 #include "nsString.h"
 #include "plstr.h"
 #include "nsIContent.h"
 #include "nsIDocument.h"
 #include "nsIXMLContentSink.h"
 #include "nsContentCID.h"
@@ -611,17 +610,18 @@ nsXBLService::AttachGlobalKeyHandler(Eve
   EventListenerManager* manager = piTarget->GetOrCreateListenerManager();
   if (!manager)
     return NS_ERROR_FAILURE;
 
   // the listener already exists, so skip this
   if (contentNode && contentNode->GetProperty(nsGkAtoms::listener))
     return NS_OK;
 
-  nsCOMPtr<nsIDOMElement> elt(do_QueryInterface(contentNode));
+  Element* elt =
+   contentNode && contentNode->IsElement() ? contentNode->AsElement() : nullptr;
 
   // Create the key handler
   RefPtr<nsXBLWindowKeyHandler> handler =
     NS_NewXBLWindowKeyHandler(elt, piTarget);
 
   handler->InstallKeyboardEventListenersTo(manager);
 
   if (contentNode)

--- a/dom/xbl/nsXBLWindowKeyHandler.cpp
+++ b/dom/xbl/nsXBLWindowKeyHandler.cpp
@@ -8,17 +8,16 @@
 #include "nsXBLPrototypeHandler.h"
 #include "nsXBLWindowKeyHandler.h"
 #include "nsIContent.h"
 #include "nsAtom.h"
 #include "nsXBLService.h"
 #include "nsIServiceManager.h"
 #include "nsGkAtoms.h"
 #include "nsXBLDocumentInfo.h"
-#include "nsIDOMElement.h"
 #include "nsFocusManager.h"
 #include "nsIURI.h"
 #include "nsNetUtil.h"
 #include "nsContentUtils.h"
 #include "nsXBLPrototypeBinding.h"
 #include "nsPIDOMWindow.h"
 #include "nsIDocShell.h"
 #include "nsIDOMDocument.h"
@@ -157,17 +156,17 @@ uint32_t nsXBLWindowKeyHandler::sRefCnt 
 nsXBLWindowKeyHandler::EnsureSpecialDocInfo()
 {
   if (!sXBLSpecialDocInfo) {
     sXBLSpecialDocInfo = new nsXBLSpecialDocInfo();
   }
   sXBLSpecialDocInfo->LoadDocInfo();
 }
 
-nsXBLWindowKeyHandler::nsXBLWindowKeyHandler(nsIDOMElement* aElement,
+nsXBLWindowKeyHandler::nsXBLWindowKeyHandler(Element* aElement,
                                              EventTarget* aTarget)
   : mTarget(aTarget),
     mHandler(nullptr),
     mUserHandler(nullptr)
 {
   mWeakPtrForElement = do_GetWeakReference(aElement);
   ++sRefCnt;
 }
@@ -948,14 +947,14 @@ nsXBLWindowKeyHandler::IsExecutableEleme
   }
 
   return true;
 }
 
 ///////////////////////////////////////////////////////////////////////////////////
 
 already_AddRefed<nsXBLWindowKeyHandler>
-NS_NewXBLWindowKeyHandler(nsIDOMElement* aElement, EventTarget* aTarget)
+NS_NewXBLWindowKeyHandler(Element* aElement, EventTarget* aTarget)
 {
   RefPtr<nsXBLWindowKeyHandler> result =
     new nsXBLWindowKeyHandler(aElement, aTarget);
   return result.forget();
 }

--- a/dom/xbl/nsXBLWindowKeyHandler.h
+++ b/dom/xbl/nsXBLWindowKeyHandler.h
@@ -8,17 +8,16 @@
 #define nsXBLWindowKeyHandler_h__
 
 #include "mozilla/EventForwards.h"
 #include "mozilla/layers/KeyboardMap.h"
 #include "nsWeakPtr.h"
 #include "nsIDOMEventListener.h"
 
 class nsAtom;
-class nsIDOMElement;
 class nsXBLPrototypeHandler;
 
 namespace mozilla {
 class EventListenerManager;
 class WidgetKeyboardEvent;
 struct IgnoreModifierState;
 namespace dom {
 class Element;
@@ -30,17 +29,18 @@ class KeyboardEvent;
 class nsXBLWindowKeyHandler : public nsIDOMEventListener
 {
   typedef mozilla::EventListenerManager EventListenerManager;
   typedef mozilla::IgnoreModifierState IgnoreModifierState;
   typedef mozilla::layers::KeyboardMap KeyboardMap;
   typedef mozilla::dom::KeyboardEvent KeyboardEvent;
 
 public:
-  nsXBLWindowKeyHandler(nsIDOMElement* aElement, mozilla::dom::EventTarget* aTarget);
+  nsXBLWindowKeyHandler(mozilla::dom::Element* aElement,
+                        mozilla::dom::EventTarget* aTarget);
 
   void InstallKeyboardEventListenersTo(
          EventListenerManager* aEventListenerManager);
   void RemoveKeyboardEventListenersFrom(
          EventListenerManager* aEventListenerManager);
 
   static KeyboardMap CollectKeyboardShortcuts();
 
@@ -133,12 +133,12 @@ protected:
   nsXBLPrototypeHandler* mHandler;     // platform bindings
   nsXBLPrototypeHandler* mUserHandler; // user-specific bindings
 
   // holds reference count to document info about bindings
   static uint32_t sRefCnt;
 };
 
 already_AddRefed<nsXBLWindowKeyHandler>
-NS_NewXBLWindowKeyHandler(nsIDOMElement* aElement,
+NS_NewXBLWindowKeyHandler(mozilla::dom::Element* aElement,
                           mozilla::dom::EventTarget* aTarget);
 
 #endif

--- a/dom/xml/XMLDocument.cpp
+++ b/dom/xml/XMLDocument.cpp
@@ -10,17 +10,16 @@
 #include "nsCharsetSource.h"
 #include "nsIXMLContentSink.h"
 #include "nsPresContext.h"
 #include "nsIContent.h"
 #include "nsIContentViewer.h"
 #include "nsIDocShell.h"
 #include "nsHTMLParts.h"
 #include "nsIComponentManager.h"
-#include "nsIDOMElement.h"
 #include "nsIBaseWindow.h"
 #include "nsIDOMWindow.h"
 #include "nsCOMPtr.h"
 #include "nsString.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsIURI.h"
 #include "nsIServiceManager.h"
 #include "nsNetUtil.h"

--- a/dom/xml/nsXMLPrettyPrinter.cpp
+++ b/dom/xml/nsXMLPrettyPrinter.cpp
@@ -4,17 +4,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsXMLPrettyPrinter.h"
 #include "nsContentUtils.h"
 #include "nsICSSDeclaration.h"
 #include "nsIObserver.h"
 #include "nsSyncLoadService.h"
 #include "nsPIDOMWindow.h"
-#include "nsIDOMElement.h"
 #include "nsIServiceManager.h"
 #include "nsNetUtil.h"
 #include "mozilla/dom/Element.h"
 #include "nsBindingManager.h"
 #include "nsXBLService.h"
 #include "nsIScriptSecurityManager.h"
 #include "mozilla/Preferences.h"
 #include "nsIDocument.h"

--- a/dom/xslt/xpath/txMozillaXPathTreeWalker.cpp
+++ b/dom/xslt/xpath/txMozillaXPathTreeWalker.cpp
@@ -2,17 +2,16 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "txXPathTreeWalker.h"
 #include "nsAtom.h"
 #include "nsIAttribute.h"
 #include "nsIDOMDocument.h"
-#include "nsIDOMElement.h"
 #include "nsINode.h"
 #include "nsPrintfCString.h"
 #include "nsReadableUtils.h"
 #include "nsString.h"
 #include "nsTextFragment.h"
 #include "txXMLUtils.h"
 #include "txLog.h"
 #include "nsUnicharUtils.h"

--- a/dom/xslt/xslt/txMozillaXSLTProcessor.cpp
+++ b/dom/xslt/xslt/txMozillaXSLTProcessor.cpp
@@ -3,17 +3,16 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "txMozillaXSLTProcessor.h"
 #include "nsContentCID.h"
 #include "nsError.h"
 #include "nsIChannel.h"
 #include "mozilla/dom/Element.h"
-#include "nsIDOMElement.h"
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsIIOService.h"
 #include "nsILoadGroup.h"
 #include "nsIStringBundle.h"
 #include "nsIURI.h"
 #include "nsMemory.h"
 #include "XPathResult.h"

--- a/dom/xul/nsXULCommandDispatcher.cpp
+++ b/dom/xul/nsXULCommandDispatcher.cpp
@@ -9,17 +9,16 @@
   This file provides the implementation for the XUL Command Dispatcher.
 
  */
 
 #include "nsIContent.h"
 #include "nsFocusManager.h"
 #include "nsIControllers.h"
 #include "nsIDOMDocument.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMWindow.h"
 #include "nsIDocument.h"
 #include "nsPresContext.h"
 #include "nsIPresShell.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsPIDOMWindow.h"
 #include "nsPIWindowRoot.h"
 #include "nsRDFCID.h"

--- a/dom/xul/nsXULContentUtils.cpp
+++ b/dom/xul/nsXULContentUtils.cpp
@@ -13,17 +13,16 @@
 
 #include "mozilla/ArrayUtils.h"
 
 #include "nsCollationCID.h"
 #include "nsCOMPtr.h"
 #include "nsIContent.h"
 #include "nsICollation.h"
 #include "nsIDocument.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMXULCommandDispatcher.h"
 #include "nsIRDFService.h"
 #include "nsIServiceManager.h"
 #include "nsXULContentUtils.h"
 #include "nsLayoutCID.h"
 #include "nsRDFCID.h"
 #include "nsString.h"
 #include "nsGkAtoms.h"

--- a/dom/xul/nsXULControllers.cpp
+++ b/dom/xul/nsXULControllers.cpp
@@ -8,17 +8,16 @@
   This file provides the implementation for the XUL "controllers"
   object.
 
 */
 
 #include "nsString.h"
 
 #include "nsIControllers.h"
-#include "nsIDOMElement.h"
 #include "nsXULControllers.h"
 #include "nsIController.h"
 
 //----------------------------------------------------------------------
 
 nsXULControllers::nsXULControllers()
 : mCurControllerID(0)
 {

--- a/dom/xul/nsXULElement.h
+++ b/dom/xul/nsXULElement.h
@@ -645,21 +645,16 @@ protected:
     ~nsXULElement();
 
     // This can be removed if EnsureContentsGenerated dies.
     friend class nsNSElementTearoff;
 
     // Implementation methods
     nsresult EnsureContentsGenerated(void) const;
 
-    nsresult ExecuteOnBroadcastHandler(nsIDOMElement* anElement, const nsAString& attrName);
-
-    static nsresult
-    ExecuteJSCode(nsIDOMElement* anElement, mozilla::WidgetEvent* aEvent);
-
     // Helper routine that crawls a parent chain looking for a tree element.
     NS_IMETHOD GetParentTree(nsIDOMXULMultiSelectControlElement** aTreeElement);
 
     nsresult AddPopupListener(nsAtom* aName);
 
     void LoadSrc();
 
     /**

--- a/dom/xul/nsXULPopupListener.cpp
+++ b/dom/xul/nsXULPopupListener.cpp
@@ -215,17 +215,16 @@ nsXULPopupListener::HandleEvent(Event* a
 
 #ifndef NS_CONTEXT_MENU_IS_MOUSEUP
 nsresult
 nsXULPopupListener::FireFocusOnTargetContent(nsIDOMNode* aTargetNode, bool aIsTouch)
 {
   nsCOMPtr<nsIContent> content = do_QueryInterface(aTargetNode);
   nsCOMPtr<nsIDocument> doc = content->OwnerDoc();
 
-  // Get nsIDOMElement for targetNode
   // strong reference to keep this from going away between events
   // XXXbz between what events?  We don't use this local at all!
   RefPtr<nsPresContext> context = doc->GetPresContext();
   if (!context) {
     return NS_ERROR_FAILURE;
   }
 
   nsIFrame* targetFrame = content->GetPrimaryFrame();

--- a/dom/xul/nsXULPopupListener.h
+++ b/dom/xul/nsXULPopupListener.h
@@ -8,17 +8,16 @@
  */
 
 #ifndef nsXULPopupListener_h___
 #define nsXULPopupListener_h___
 
 #include "nsCOMPtr.h"
 
 #include "mozilla/dom/Element.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMEventListener.h"
 #include "nsCycleCollectionParticipant.h"
 
 namespace mozilla {
 namespace dom {
 class MouseEvent;
 } // namespace dom
 } // namespace mozilla

--- a/dom/xul/nsXULSortService.cpp
+++ b/dom/xul/nsXULSortService.cpp
@@ -4,17 +4,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /*
   This file provides the implementation for the sort service manager.
  */
 
 #include "nsCOMPtr.h"
 #include "nsIContent.h"
-#include "nsIDOMElement.h"
 #include "nsIDOMNode.h"
 #include "nsIServiceManager.h"
 #include "nsGkAtoms.h"
 #include "nsNameSpaceManager.h"
 #include "nsXULContentUtils.h"
 #include "nsString.h"
 #include "nsQuickSort.h"
 #include "nsWhitespaceTokenizer.h"