Add a deprecation warning for document.clear()

Source/core/html/HTMLDocument.idl

 /*
  * Copyright (C) 2006, 2007, 2008 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 17 matching lines @@
     [Custom, PerWorldBindings, ActivityLog=AccessForIsolatedWorlds] void writeln([Default=Undefined] optional DOMString text);
 
     readonly attribute HTMLCollection embeds;
     readonly attribute HTMLCollection plugins;
     readonly attribute HTMLCollection scripts;
 
     // Extensions
 
     [Replaceable] readonly attribute HTMLAllCollection all;
 
-    void clear();
+    [DeprecateAs=DocumentClear] void clear();
 
     readonly attribute long width;
     readonly attribute long height;
              [TreatNullAs=NullString] attribute DOMString dir;
              [TreatNullAs=NullString] attribute DOMString designMode;
     readonly attribute DOMString compatMode;
 
     readonly attribute Element activeElement;
     boolean hasFocus();
 
     // Deprecated attributes
              [TreatNullAs=NullString] attribute DOMString bgColor;
              [TreatNullAs=NullString] attribute DOMString fgColor;
              [TreatNullAs=NullString] attribute DOMString alinkColor;
              [TreatNullAs=NullString] attribute DOMString linkColor;
              [TreatNullAs=NullString] attribute DOMString vlinkColor;
 };