Oilpan: make Supplementable tracing more regular.

Source/core/workers/WorkerClients.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 32 matching lines @@
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WorkerClients);
     WTF_MAKE_NONCOPYABLE(WorkerClients);
 public:
     static PassOwnPtrWillBeRawPtr<WorkerClients> create()
     {
         return adoptPtrWillBeNoop(new WorkerClients());
     }
 
     virtual ~WorkerClients() { }
 
+#if ENABLE(OILPAN)
     virtual void trace(Visitor* visitor) OVERRIDE
     {
-        WillBeHeapSupplementable<WorkerClients>::trace(visitor);
+        HeapSupplementable<WorkerClients>::trace(visitor);
     }
+#endif
 
 private:
     WorkerClients() { }
 };
 
 } // namespace blink
 
 #endif // WorkerClients_h