Make Event RefCountedGarbageCollected and implement trace() methods to the Event hierarcy

Source/core/events/WheelEvent.cpp

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 108 matching lines @@
 bool WheelEvent::isMouseEvent() const
 {
     return false;
 }
 
 bool WheelEvent::isWheelEvent() const
 {
     return true;
 }
 
+void WheelEvent::trace(Visitor* visitor)
+{
+    MouseEvent::trace(visitor);
+}
+
 inline static unsigned deltaMode(const PlatformWheelEvent& event)
 {
     return event.granularity() == ScrollByPageWheelEvent ? WheelEvent::DOM_DELTA_PAGE : WheelEvent::DOM_DELTA_PIXEL;
 }
 
 PassRefPtr<WheelEventDispatchMediator> WheelEventDispatchMediator::create(const PlatformWheelEvent& event, PassRefPtr<AbstractView> view)
 {
     return adoptRef(new WheelEventDispatchMediator(event, view));
 }
 
@@ skipping 12 matching lines @@
     return toWheelEvent(EventDispatchMediator::event());
 }
 
 bool WheelEventDispatchMediator::dispatchEvent(EventDispatcher* dispatcher) const
 {
     ASSERT(event());
     return EventDispatchMediator::dispatchEvent(dispatcher) && !event()->defaultHandled();
 }
 
 } // namespace WebCore