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

third_party/WebKit/Source/core/dom/custom/CustomElementProcessingStack.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
@@ skipping 24 matching lines @@
 
 namespace blink {
 
 size_t CustomElementProcessingStack::s_elementQueueStart = 0;
 
 // The base of the stack has a null sentinel value.
 size_t CustomElementProcessingStack::s_elementQueueEnd = kNumSentinels;
 
 CustomElementProcessingStack& CustomElementProcessingStack::instance()
 {
-    DEFINE_STATIC_LOCAL(Persistent<CustomElementProcessingStack>, instance, (new CustomElementProcessingStack()));
-    return *instance;
+    DEFINE_STATIC_LOCAL(CustomElementProcessingStack, instance, (new CustomElementProcessingStack));
+    return instance;
 }
 
 // Dispatches callbacks when popping the processing stack.
 void CustomElementProcessingStack::processElementQueueAndPop()
 {
     instance().processElementQueueAndPop(s_elementQueueStart, s_elementQueueEnd);
 }
 
 void CustomElementProcessingStack::processElementQueueAndPop(size_t start, size_t end)
 {
@@ skipping 32 matching lines @@
     m_flattenedProcessingStack.append(callbackQueue);
     ++s_elementQueueEnd;
 }
 
 DEFINE_TRACE(CustomElementProcessingStack)
 {
     visitor->trace(m_flattenedProcessingStack);
 }
 
 } // namespace blink