Document the ClientRect* vs DOMRect* situation

Source/core/dom/ClientRectList.h

 /*
  * Copyright (C) 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 34 matching lines @@
     static PassRefPtrWillBeRawPtr<ClientRectList> create()
     {
         return adoptRefWillBeNoop(new ClientRectList);
     }
     static PassRefPtrWillBeRawPtr<ClientRectList> create(const Vector<FloatQuad>& quads)
     {
         return adoptRefWillBeNoop(new ClientRectList(quads));
     }
     unsigned length() const;
     ClientRect* item(unsigned index);
+    ClientRect* anonymousIndexedGetter(unsigned index) { return item(index); }
 
     DECLARE_TRACE();
 
 private:
     ClientRectList();
     explicit ClientRectList(const Vector<FloatQuad>&);
 
     WillBeHeapVector<RefPtrWillBeMember<ClientRect> > m_list;
 };
 
 } // namespace blink
 
 #endif // ClientRectList_h