Measure the usage of prefixed Shadow DOM APIs.

Source/core/dom/Element.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 88 matching lines @@
 
     // WebKit extension, pending specification.
     [RaisesException] boolean webkitMatchesSelector([Default=Undefined] optional DOMString selectors);
 
     // Shadow DOM API
     [EnabledAtRuntime=experimentalShadowDOM, Reflect, PerWorldBindings] attribute DOMString pseudo;
     [EnabledAtRuntime=experimentalShadowDOM, RaisesException] ShadowRoot createShadowRoot();
     [EnabledAtRuntime=experimentalShadowDOM, PerWorldBindings] readonly attribute ShadowRoot shadowRoot;
 
     // To-be-deprecated prefixed Shadow DOM API
-    [Reflect=pseudo, ImplementedAs=pseudo, PerWorldBindings] attribute DOMString webkitPseudo;
-    [ImplementedAs=createShadowRoot, RaisesException] ShadowRoot webkitCreateShadowRoot();
-    [ImplementedAs=shadowRoot, PerWorldBindings] readonly attribute ShadowRoot webkitShadowRoot;
+    [Reflect=pseudo, ImplementedAs=pseudo, PerWorldBindings, MeasureAs=ShadowDOMPrefixedPseudo] attribute DOMString webkitPseudo;
+    [ImplementedAs=createShadowRoot, RaisesException, MeasureAs=ShadowDOMPrefixedCreateShadowRoot] ShadowRoot webkitCreateShadowRoot();
+    [ImplementedAs=shadowRoot, PerWorldBindings, MeasureAs=ShadowDOMPrefixedShadowRoot] readonly attribute ShadowRoot webkitShadowRoot;
 
     // CSSOM View Module API
     ClientRectList getClientRects();
     ClientRect getBoundingClientRect();
 
     // Mozilla version
     const unsigned short ALLOW_KEYBOARD_INPUT = 1;
     [EnabledAtRuntime=fullscreen] void webkitRequestFullScreen([Default=Undefined] optional unsigned short flags);
 
     // W3C version
@@ skipping 76 matching lines @@
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventListener ontouchmove;
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventListener ontouchend;
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventListener ontouchcancel;
     [NotEnumerable, PerWorldBindings] attribute EventListener onwebkitfullscreenchange;
     [NotEnumerable, PerWorldBindings] attribute EventListener onwebkitfullscreenerror;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;