Improve DEFINE_STATIC_LOCAL()'s handling of Blink GCed objects.

third_party/WebKit/Source/core/dom/ChildListMutationScope.cpp

 /*
  * Copyright (C) 2011 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 28 matching lines @@
 namespace blink {
 
 // The accumulator map is used to make sure that there is only one mutation
 // accumulator for a given node even if there are multiple ChildListMutationScopes
 // on the stack. The map is always empty when there are no ChildListMutationScopes
 // on the stack.
 typedef HeapHashMap<Member<Node>, Member<ChildListMutationAccumulator>> AccumulatorMap;
 
 static AccumulatorMap& accumulatorMap()
 {
-    DEFINE_STATIC_LOCAL(Persistent<AccumulatorMap>, map, (new AccumulatorMap()));
-    return *map;
+    DEFINE_STATIC_LOCAL(AccumulatorMap, map, (new AccumulatorMap));
+    return map;
 }
 
 ChildListMutationAccumulator::ChildListMutationAccumulator(RawPtr<Node> target, RawPtr<MutationObserverInterestGroup> observers)
     : m_target(target)
     , m_lastAdded(nullptr)
     , m_observers(observers)
     , m_mutationScopes(0)
 {
 }
 
@@ skipping 99 matching lines @@
     visitor->trace(m_target);
     visitor->trace(m_removedNodes);
     visitor->trace(m_addedNodes);
     visitor->trace(m_previousSibling);
     visitor->trace(m_nextSibling);
     visitor->trace(m_lastAdded);
     visitor->trace(m_observers);
 }
 
 } // namespace blink