Oilpan: Prepare to move IdTargetObserver and IdTargetObserverRegistry to Oilpan heap.

Source/core/dom/IdTargetObserver.cpp

 /*
  * Copyright (C) 2012 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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/dom/IdTargetObserver.h"
 
 #include "core/dom/IdTargetObserverRegistry.h"
 
 namespace WebCore {
 
-IdTargetObserver::IdTargetObserver(IdTargetObserverRegistry& registry, const AtomicString& id)
-    : m_registry(registry)
+IdTargetObserver::IdTargetObserver(IdTargetObserverRegistry& observerRegistry, const AtomicString& id)
+    : m_registry(&observerRegistry)
     , m_id(id)
 {
-    m_registry.addObserver(m_id, this);
+    registry().addObserver(m_id, this);
 }
 
 IdTargetObserver::~IdTargetObserver()
 {
 #if !ENABLE(OILPAN)
-    m_registry.removeObserver(m_id, this);
+    registry().removeObserver(m_id, this);
 #endif
 }
 
+void IdTargetObserver::trace(Visitor* visitor)
+{
+    visitor->trace(m_registry);
+}
+
 void IdTargetObserver::unregister()
 {
 #if ENABLE(OILPAN)
-    m_registry.removeObserver(m_id, this);
+    registry().removeObserver(m_id, this);
 #endif
 }
 
 } // namespace WebCore