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

third_party/WebKit/Source/core/dom/MutationObserver.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 148 matching lines @@
 }
 
 void MutationObserver::observationEnded(MutationObserverRegistration* registration)
 {
     ASSERT(m_registrations.contains(registration));
     m_registrations.remove(registration);
 }
 
 static MutationObserverSet& activeMutationObservers()
 {
-    DEFINE_STATIC_LOCAL(Persistent<MutationObserverSet>, activeObservers, (new MutationObserverSet()));
-    return *activeObservers;
+    DEFINE_STATIC_LOCAL(MutationObserverSet, activeObservers, (new MutationObserverSet));
+    return activeObservers;
 }
 
 static MutationObserverSet& suspendedMutationObservers()
 {
-    DEFINE_STATIC_LOCAL(Persistent<MutationObserverSet>, suspendedObservers, (new MutationObserverSet()));
-    return *suspendedObservers;
+    DEFINE_STATIC_LOCAL(MutationObserverSet, suspendedObservers, (new MutationObserverSet));
+    return suspendedObservers;
 }
 
 static void activateObserver(RawPtr<MutationObserver> observer)
 {
     if (activeMutationObservers().isEmpty())
         Microtask::enqueueMicrotask(WTF::bind(&MutationObserver::deliverMutations));
 
     activeMutationObservers().add(observer);
 }
 
@@ skipping 84 matching lines @@
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_callback);
     visitor->trace(m_records);
     visitor->trace(m_registrations);
     visitor->trace(m_callback);
 #endif
 }
 
 } // namespace blink