Make Window.offscreenBuffering non-enumerable

Source/core/frame/Window.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 62 matching lines @@
                       optional DOMString defaultValue = "");
 
     boolean find([Default=Undefined] optional DOMString string,
                  [Default=Undefined] optional boolean caseSensitive,
                  [Default=Undefined] optional boolean backwards,
                  [Default=Undefined] optional boolean wrap,
                  [Default=Undefined] optional boolean wholeWord,
                  [Default=Undefined] optional boolean searchInFrames,
                  [Default=Undefined] optional boolean showDialog);
 
-    [Replaceable, MeasureAs=WindowOffscreenBuffering] readonly attribute boolean offscreenBuffering;
+    [Replaceable, MeasureAs=WindowOffscreenBuffering, NotEnumerable] readonly attribute boolean offscreenBuffering;
 
     [Replaceable] readonly attribute long outerHeight;
     [Replaceable] readonly attribute long outerWidth;
     [Replaceable] readonly attribute long innerHeight;
     [Replaceable] readonly attribute long innerWidth;
     [Replaceable] readonly attribute long screenX;
     [Replaceable] readonly attribute long screenY;
     [Replaceable] readonly attribute long screenLeft;
     [Replaceable] readonly attribute long screenTop;
     [Replaceable] readonly attribute double scrollX;
@@ skipping 122 matching lines @@
 // FIXME: make this typedef accurate once enough of http://crbug.com/240176
 // is in place.
 // FIXME: consider putting this typedef in an .idl file containing spec-wide
 // utility type definitions.
 typedef MessagePort Transferable;
 
 Window implements GlobalEventHandlers;
 Window implements WindowBase64;
 Window implements WindowEventHandlers;
 Window implements WindowTimers;