Add a UseCounter for HTMLElement.webkitdropzone

Source/core/html/HTMLElement.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 10 matching lines @@
 [
     Custom=Wrap,
 ] interface HTMLElement : Element {
     [Reflect] attribute DOMString title;
     [Reflect] attribute DOMString lang;
     attribute boolean translate;
     attribute DOMString dir;
 
     [CustomElementCallbacks] attribute long              tabIndex;
     [CustomElementCallbacks] attribute boolean           draggable;
-    [Reflect, TreatNullAs=NullString] attribute DOMString webkitdropzone;
+    [Reflect, TreatNullAs=NullString, MeasureAs=PrefixedHTMLElementDropzone] attribute DOMString webkitdropzone;
     [Reflect] attribute boolean hidden;
     [Reflect] attribute DOMString accessKey;
 
     // Extensions
     [TreatNullAs=NullString, CustomElementCallbacks, RaisesException=Setter, MeasureAs=HTMLElementInnerText] attribute DOMString innerText;
     [TreatNullAs=NullString, CustomElementCallbacks, RaisesException=Setter, MeasureAs=HTMLElementOuterText] attribute DOMString outerText;
 
     [RuntimeEnabled=IMEAPI] readonly attribute InputMethodContext inputMethodContext;
 
     [CustomElementCallbacks, RaisesException=Setter] attribute DOMString contentEditable;
     readonly attribute boolean isContentEditable;
 
              attribute boolean spellcheck;
 
     void click();
 };
 
 HTMLElement implements GlobalEventHandlers;