Oilpan: make Supplementable tracing more regular.

Source/platform/RefCountedSupplement.h

 /*
  * Copyright (C) 2012 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 31 matching lines @@
 
     class Wrapper FINAL : public Supplement<T> {
     public:
         explicit Wrapper(PassRefPtr<ThisType> wrapped) : m_wrapped(wrapped) { }
         virtual ~Wrapper() { }
 #if ENABLE(SECURITY_ASSERT)
         virtual bool isRefCountedWrapper() const OVERRIDE { return true; }
 #endif
         ThisType* wrapped() const { return m_wrapped.get(); }
 
-        virtual void trace(Visitor*) OVERRIDE { }
-
     private:
 
         RefPtr<ThisType> m_wrapped;
     };
 
     static void provideTo(Supplementable<T>& host, const char* key, PassRefPtr<ThisType> supplement)
     {
         host.provideSupplement(key, adoptPtr(new Wrapper(supplement)));
     }
 
     static ThisType* from(Supplementable<T>& host, const char* key)
     {
         Supplement<T>* found = static_cast<Supplement<T>*>(host.requireSupplement(key));
         if (!found)
             return 0;
         ASSERT_WITH_SECURITY_IMPLICATION(found->isRefCountedWrapper());
         return static_cast<Wrapper*>(found)->wrapped();
     }
 };
 #endif
 
 } // namespace blink
 
 #endif // RefCountedSupplement_h