--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -13,17 +13,16 @@
 #include "mozilla/MathAlgorithms.h"
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/dom/MediaEncryptedEvent.h"
 #include "mozilla/EMEUtils.h"
 #include "mozilla/Sprintf.h"
 
 #include "base/basictypes.h"
 #include "nsIDOMHTMLMediaElement.h"
-#include "nsIDOMHTMLSourceElement.h"
 #include "TimeRanges.h"
 #include "nsGenericHTMLElement.h"
 #include "nsAttrValueInlines.h"
 #include "nsDocShellLoadTypes.h"
 #include "nsPresContext.h"
 #include "nsIClassOfService.h"
 #include "nsIPresShell.h"
 #include "nsGkAtoms.h"

--- a/dom/html/HTMLSourceElement.cpp
+++ b/dom/html/HTMLSourceElement.cpp
@@ -30,31 +30,20 @@ HTMLSourceElement::HTMLSourceElement(alr
 
 HTMLSourceElement::~HTMLSourceElement()
 {
 }
 
 NS_IMPL_CYCLE_COLLECTION_INHERITED(HTMLSourceElement, nsGenericHTMLElement,
                                    mSrcMediaSource)
 
-NS_IMPL_ADDREF_INHERITED(HTMLSourceElement, nsGenericHTMLElement)
-NS_IMPL_RELEASE_INHERITED(HTMLSourceElement, nsGenericHTMLElement)
-
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(HTMLSourceElement)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMHTMLSourceElement)
-NS_INTERFACE_MAP_END_INHERITING(nsGenericHTMLElement)
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(HTMLSourceElement, nsGenericHTMLElement)
 
 NS_IMPL_ELEMENT_CLONE(HTMLSourceElement)
 
-NS_IMPL_URI_ATTR(HTMLSourceElement, Src, src)
-NS_IMPL_STRING_ATTR(HTMLSourceElement, Type, type)
-NS_IMPL_STRING_ATTR(HTMLSourceElement, Srcset, srcset)
-NS_IMPL_STRING_ATTR(HTMLSourceElement, Sizes, sizes)
-NS_IMPL_STRING_ATTR(HTMLSourceElement, Media, media)
-
 bool
 HTMLSourceElement::MatchesCurrentMedia()
 {
   if (mMediaList) {
     nsIPresShell* presShell = OwnerDoc()->GetShell();
     nsPresContext* pctx = presShell ? presShell->GetPresContext() : nullptr;
     return pctx && mMediaList->Matches(pctx);
   }

--- a/dom/html/HTMLSourceElement.h
+++ b/dom/html/HTMLSourceElement.h
@@ -3,43 +3,38 @@
 /* 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/. */
 
 #ifndef mozilla_dom_HTMLSourceElement_h
 #define mozilla_dom_HTMLSourceElement_h
 
 #include "mozilla/Attributes.h"
-#include "nsIDOMHTMLSourceElement.h"
 #include "nsGenericHTMLElement.h"
 #include "mozilla/dom/HTMLMediaElement.h"
 
 class nsAttrValue;
 
 namespace mozilla {
 namespace dom {
 
 class MediaList;
 
-class HTMLSourceElement final : public nsGenericHTMLElement,
-                                public nsIDOMHTMLSourceElement
+class HTMLSourceElement final : public nsGenericHTMLElement
 {
 public:
   explicit HTMLSourceElement(already_AddRefed<mozilla::dom::NodeInfo>& aNodeInfo);
 
   // nsISupports
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(HTMLSourceElement,
                                            nsGenericHTMLElement)
 
   NS_IMPL_FROMCONTENT_HTML_WITH_TAG(HTMLSourceElement, source)
 
-  // nsIDOMHTMLSourceElement
-  NS_DECL_NSIDOMHTMLSOURCEELEMENT
-
   virtual nsresult Clone(mozilla::dom::NodeInfo* aNodeInfo, nsINode** aResult,
                          bool aPreallocateChildren) const override;
 
   // Override BindToTree() so that we can trigger a load when we add a
   // child source element.
   virtual nsresult BindToTree(nsIDocument* aDocument, nsIContent* aParent,
                               nsIContent* aBindingParent,
                               bool aCompileEventHandlers) override;

--- a/dom/html/HTMLVideoElement.cpp
+++ b/dom/html/HTMLVideoElement.cpp
@@ -1,15 +1,14 @@
 /* -*- 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 "nsIDOMHTMLSourceElement.h"
 #include "mozilla/dom/HTMLVideoElement.h"
 #include "mozilla/dom/HTMLVideoElementBinding.h"
 #include "nsGenericHTMLElement.h"
 #include "nsGkAtoms.h"
 #include "nsSize.h"
 #include "nsError.h"
 #include "nsNodeInfoManager.h"
 #include "plbase64.h"

--- a/dom/interfaces/html/moz.build
+++ b/dom/interfaces/html/moz.build
@@ -15,17 +15,16 @@ XPIDL_SOURCES += [
     'nsIDOMHTMLFormElement.idl',
     'nsIDOMHTMLHtmlElement.idl',
     'nsIDOMHTMLInputElement.idl',
     'nsIDOMHTMLMediaElement.idl',
     'nsIDOMHTMLOptionElement.idl',
     'nsIDOMHTMLOptionsCollection.idl',
     'nsIDOMHTMLScriptElement.idl',
     'nsIDOMHTMLSelectElement.idl',
-    'nsIDOMHTMLSourceElement.idl',
     'nsIDOMMozBrowserFrame.idl',
     'nsIDOMTimeRanges.idl',
     'nsIDOMValidityState.idl',
     'nsIMozBrowserFrame.idl',
 ]
 
 XPIDL_MODULE = 'dom_html'
 

deleted file mode 100644
--- a/dom/interfaces/html/nsIDOMHTMLSourceElement.idl
+++ /dev/null
@@ -1,27 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim:set ts=2 sw=2 sts=2 et cindent: */
-/* 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 "nsIDOMHTMLElement.idl"
-
-/**
- * The nsIDOMHTMLSourceElement interface is the interface to a HTML
- * <source> element.
- *
- * For more information on this interface, please see
- * http://www.whatwg.org/specs/web-apps/current-work/#source
- *
- * @status UNDER_DEVELOPMENT
- */
-
-[uuid(1deb68f8-2ed6-4a41-b8c8-e0f86510f799)]
-interface nsIDOMHTMLSourceElement : nsISupports
-{
-           attribute DOMString src;
-           attribute DOMString type;
-           attribute DOMString srcset;
-           attribute DOMString sizes;
-           attribute DOMString media;
-};

--- a/dom/webbrowserpersist/WebBrowserPersistLocalDocument.cpp
+++ b/dom/webbrowserpersist/WebBrowserPersistLocalDocument.cpp
@@ -26,17 +26,16 @@
 #include "nsIDOMDocument.h"
 #include "nsIDOMHTMLBaseElement.h"
 #include "nsIDOMHTMLCollection.h"
 #include "nsIDOMHTMLDocument.h"
 #include "nsIDOMHTMLInputElement.h"
 #include "nsIDOMHTMLMediaElement.h"
 #include "nsIDOMHTMLOptionElement.h"
 #include "nsIDOMHTMLScriptElement.h"
-#include "nsIDOMHTMLSourceElement.h"
 #include "nsIDOMMozNamedAttrMap.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMNodeFilter.h"
 #include "nsIDOMNodeList.h"
 #include "nsIDOMProcessingInstruction.h"
 #include "nsIDOMTreeWalker.h"
 #include "nsIDOMWindowUtils.h"
 #include "nsIDocShell.h"
@@ -489,18 +488,18 @@ ResourceReader::OnWalkDOMNode(nsIDOMNode
     if (content->IsSVGElement(nsGkAtoms::img)) {
         return OnWalkAttribute(aNode, "href", "http://www.w3.org/1999/xlink");
     }
 
     nsCOMPtr<nsIDOMHTMLMediaElement> nodeAsMedia = do_QueryInterface(aNode);
     if (nodeAsMedia) {
         return OnWalkAttribute(aNode, "src");
     }
-    nsCOMPtr<nsIDOMHTMLSourceElement> nodeAsSource = do_QueryInterface(aNode);
-    if (nodeAsSource) {
+
+    if (content->IsHTMLElement(nsGkAtoms::source)) {
         return OnWalkAttribute(aNode, "src");
     }
 
     if (content->IsHTMLElement(nsGkAtoms::body)) {
         return OnWalkAttribute(aNode, "background");
     }
 
     if (content->IsHTMLElement(nsGkAtoms::table)) {
@@ -1004,18 +1003,17 @@ PersistNodeFixup::FixupNode(nsIDOMNode *
     if (nodeAsMedia) {
         rv = GetNodeToFixup(aNodeIn, aNodeOut);
         if (NS_SUCCEEDED(rv) && *aNodeOut) {
             FixupAttribute(*aNodeOut, "src");
         }
         return rv;
     }
 
-    nsCOMPtr<nsIDOMHTMLSourceElement> nodeAsSource = do_QueryInterface(aNodeIn);
-    if (nodeAsSource) {
+    if (content->IsHTMLElement(nsGkAtoms::source)) {
         rv = GetNodeToFixup(aNodeIn, aNodeOut);
         if (NS_SUCCEEDED(rv) && *aNodeOut) {
             FixupAttribute(*aNodeOut, "src");
         }
         return rv;
     }
 
     if (content->IsSVGElement(nsGkAtoms::img)) {

--- a/xpcom/reflect/xptinfo/ShimInterfaceInfo.cpp
+++ b/xpcom/reflect/xptinfo/ShimInterfaceInfo.cpp
@@ -52,17 +52,16 @@
 #include "nsIDOMHTMLFormElement.h"
 #include "nsIDOMHTMLHtmlElement.h"
 #include "nsIDOMHTMLInputElement.h"
 #include "nsIDOMHTMLMediaElement.h"
 #include "nsIDOMHTMLOptionElement.h"
 #include "nsIDOMHTMLOptionsCollection.h"
 #include "nsIDOMHTMLScriptElement.h"
 #include "nsIDOMHTMLSelectElement.h"
-#include "nsIDOMHTMLSourceElement.h"
 #include "nsIDOMKeyEvent.h"
 #include "nsIDOMMediaList.h"
 #include "nsIDOMMouseEvent.h"
 #include "nsIDOMMouseScrollEvent.h"
 #include "nsIDOMMutationEvent.h"
 #include "nsIDOMMozNamedAttrMap.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMNodeIterator.h"
@@ -156,17 +155,16 @@
 #include "mozilla/dom/HTMLHtmlElementBinding.h"
 #include "mozilla/dom/HTMLInputElementBinding.h"
 #include "mozilla/dom/HTMLMediaElementBinding.h"
 #include "mozilla/dom/HTMLObjectElementBinding.h"
 #include "mozilla/dom/HTMLOptionElementBinding.h"
 #include "mozilla/dom/HTMLOptionsCollectionBinding.h"
 #include "mozilla/dom/HTMLScriptElementBinding.h"
 #include "mozilla/dom/HTMLSelectElementBinding.h"
-#include "mozilla/dom/HTMLSourceElementBinding.h"
 #include "mozilla/dom/KeyEventBinding.h"
 #include "mozilla/dom/ListBoxObjectBinding.h"
 #include "mozilla/dom/MediaListBinding.h"
 #include "mozilla/dom/MessageEventBinding.h"
 #include "mozilla/dom/MenuBoxObjectBinding.h"
 #include "mozilla/dom/MouseEventBinding.h"
 #include "mozilla/dom/MouseScrollEventBinding.h"
 #include "mozilla/dom/MutationEventBinding.h"
@@ -311,17 +309,16 @@ const ComponentsInterfaceShimEntry kComp
   DEFINE_SHIM(HTMLFormElement),
   DEFINE_SHIM(HTMLHtmlElement),
   DEFINE_SHIM(HTMLInputElement),
   DEFINE_SHIM(HTMLMediaElement),
   DEFINE_SHIM(HTMLOptionElement),
   DEFINE_SHIM(HTMLOptionsCollection),
   DEFINE_SHIM(HTMLScriptElement),
   DEFINE_SHIM(HTMLSelectElement),
-  DEFINE_SHIM(HTMLSourceElement),
   DEFINE_SHIM(KeyEvent),
   DEFINE_SHIM_WITH_CUSTOM_INTERFACE(nsIListBoxObject, ListBoxObject),
   DEFINE_SHIM(MediaList),
   DEFINE_SHIM_WITH_CUSTOM_INTERFACE(nsIMenuBoxObject, MenuBoxObject),
   DEFINE_SHIM(MouseEvent),
   DEFINE_SHIM(MouseScrollEvent),
   DEFINE_SHIM(MutationEvent),
   DEFINE_SHIM_WITH_CUSTOM_INTERFACE(nsIDOMMozNamedAttrMap, NamedNodeMap),