Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/dom/EventHandlerRegistry.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EventHandlerRegistry_h
 #define EventHandlerRegistry_h
 
 #include "core/dom/DocumentSupplementable.h"
 #include "core/events/Event.h"
 #include "wtf/HashCountedSet.h"
@@ skipping 31 matching lines @@
 
     // Registration and management of event handlers attached to EventTargets.
     void didAddEventHandler(EventTarget&, const AtomicString& eventType);
     void didAddEventHandler(EventTarget&, EventHandlerClass);
     void didRemoveEventHandler(EventTarget&, const AtomicString& eventType);
     void didRemoveEventHandler(EventTarget&, EventHandlerClass);
     void didMoveFromOtherDocument(EventTarget&, Document& oldDocument);
     void didRemoveAllEventHandlers(EventTarget&);
 
     virtual void trace(Visitor*) OVERRIDE { }
+    void clearWeakMembers(Visitor*);
 
 private:
     explicit EventHandlerRegistry(Document&);
 
     enum ChangeOperation {
         Add, // Add a new event handler.
         Remove, // Remove an existing event handler.
         RemoveAll // Remove any and all existing event handlers for a given target.
     };
 
@@ skipping 23 matching lines @@
         OwnPtr<EventTargetSet> targets;
     };
 
     Document& m_document;
     HandlerState m_eventHandlers[EventHandlerClassCount];
 };
 
 } // namespace WebCore
 
 #endif // EventHandlerRegistry_h