Oilpan: Move LifecycleNotifier's hierarchy to Oilpan's heap

Source/core/frame/DOMWindowLifecycleNotifier.cpp

 /*
  * Copyright (C) 2013 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 59 matching lines @@
         windowObserver->didRemoveEventListener(window, eventType);
 }
 
 void DOMWindowLifecycleNotifier::notifyRemoveAllEventListeners(LocalDOMWindow* window)
 {
     TemporaryChange<IterationType> scope(this->m_iterating, IteratingOverDOMWindowObservers);
     for (const auto& windowObserver : m_windowObservers)
         windowObserver->didRemoveAllEventListeners(window);
 }
 
+void DOMWindowLifecycleNotifier::trace(Visitor* visitor)
+{
+    visitor->trace(m_windowObservers);
+    LifecycleNotifier<LocalDOMWindow>::trace(visitor);
+}
+
 } // namespace blink