Oilpan: have Navigator and its supplements be on the heap by default.

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 28 matching lines @@
     explicit DOMWindowProperty(LocalFrame*);
 
     virtual void willDestroyGlobalObjectInFrame();
     virtual void willDetachGlobalObjectFromFrame();
 
     LocalFrame* frame() const { return m_frame; }
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
+    // TODO(Oilpan): when ~DOMWindowProperty is removed, check classes that derive
+    // from it. Several will then be able to derive from GarbageCollected<> instead.
 #if !ENABLE(OILPAN)
     virtual ~DOMWindowProperty();
 #endif
 
     RawPtrWillBeMember<LocalFrame> m_frame;
 
 #if !ENABLE(OILPAN)
 private:
     LocalDOMWindow* m_associatedDOMWindow;
 #endif
 };
 
 } // namespace blink
 
 #endif