Remove [PerWorldBindings] IDL attribute from non wrapper type attributes

Source/core/dom/ParentNode.idl

 /*
  * Copyright (C) 2013 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     LegacyTreatAsPartialInterface,
     NoInterfaceObject, // Always used on target of 'implements'
 ] interface ParentNode {
     [PerWorldBindings] readonly attribute HTMLCollection children;
     [PerWorldBindings] readonly attribute Element firstElementChild;
     [PerWorldBindings] readonly attribute Element lastElementChild;
-    [PerWorldBindings] readonly attribute unsigned long childElementCount;
+    readonly attribute unsigned long childElementCount;
 
     // NodeSelector - Selector API
     [RaisesException] Element querySelector(DOMString selectors);
     [RaisesException] NodeList querySelectorAll(DOMString selectors);
 };