Oilpan: Prepare to move EventQueue and its subclasses to Oilpan heap.

Source/core/events/EventQueue.h

 /*
  * Copyright (C) 2010 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 18 matching lines @@
 
 #include "platform/heap/Handle.h"
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace WebCore {
 
 class Event;
 
-class EventQueue {
+class EventQueue : public NoBaseWillBeGarbageCollectedFinalized<EventQueue> {
 public:
     virtual ~EventQueue() { }
+    virtual void trace(Visitor*) { }
     virtual bool enqueueEvent(PassRefPtrWillBeRawPtr<Event>) = 0;
     virtual bool cancelEvent(Event*) = 0;
     // The accumulated and all the future events will be discarded, no events will be dispatched anymore.
     virtual void close() = 0;
 };
 
 }
 
 #endif // EventQueue_h