Node.contains should return true for nodes in Shadow DOM.

Source/core/dom/Node.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 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 73 matching lines @@
     const unsigned short      DOCUMENT_POSITION_DISCONNECTED = 0x01;
     const unsigned short      DOCUMENT_POSITION_PRECEDING    = 0x02;
     const unsigned short      DOCUMENT_POSITION_FOLLOWING    = 0x04;
     const unsigned short      DOCUMENT_POSITION_CONTAINS     = 0x08;
     const unsigned short      DOCUMENT_POSITION_CONTAINED_BY = 0x10;
     const unsigned short      DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC = 0x20;
 
     unsigned short     compareDocumentPosition([Default=Undefined] optional Node other);
 
     // Introduced in DOM4
-    boolean contains([Default=Undefined] optional Node other);
+    [ImplementedAs=bindingsContains] boolean contains([Default=Undefined] optional Node other);
 
     // IE extensions
     [PerWorldBindings] readonly attribute Element          parentElement;
 };