Simplify DOMWindowProperty and its unregistration.

Source/core/frame/DOMWindowProperty.h

 /*
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef DOMWindowProperty_h
 #define DOMWindowProperty_h
 
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
-class LocalDOMWindow;
 class LocalFrame;
 
 class DOMWindowProperty : public WillBeGarbageCollectedMixin {
+    DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(DOMWindowProperty);
 public:
     explicit DOMWindowProperty(LocalFrame*);
 
     virtual void willDestroyGlobalObjectInFrame();
     virtual void willDetachGlobalObjectFromFrame();
 
     LocalFrame* frame() const { return m_frame; }
 
-    virtual void trace(Visitor*);
+    virtual void trace(Visitor*) { }
 
 protected:
-#if !ENABLE(OILPAN)
-    virtual ~DOMWindowProperty();
-#endif
-
     LocalFrame* m_frame;
-    RawPtrWillBeMember<LocalDOMWindow> m_associatedDOMWindow;
 };
 
 }
 
 #endif