Oilpan: Improve Oilpan support in EventContext and EventPath.

Source/core/events/NodeEventContext.cpp

 /*
  * Copyright (C) 2014 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 32 matching lines @@
 }
 
 NodeEventContext::~NodeEventContext()
 {
 }
 
 void NodeEventContext::trace(Visitor* visitor)
 {
     visitor->trace(m_node);
     visitor->trace(m_currentTarget);
+    visitor->trace(m_treeScopeEventContext);
 }
 
 void NodeEventContext::handleLocalEvents(Event* event) const
 {
     if (touchEventContext()) {
         touchEventContext()->handleLocalEvents(event);
     } else if (relatedTarget()) {
         if (event->isMouseEvent()) {
             toMouseEvent(event)->setRelatedTarget(relatedTarget());
         } else if (event->isFocusEvent()) {
             toFocusEvent(event)->setRelatedTarget(relatedTarget());
         }
     }
     event->setTarget(target());
     event->setCurrentTarget(m_currentTarget.get());
     m_node->handleLocalEvents(event);
 }
 
 }