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

third_party/WebKit/Source/core/dom/shadow/ShadowRoot.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.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 279 matching lines @@
 }
 
 void ShadowRoot::invalidateDescendantInsertionPoints()
 {
     m_descendantInsertionPointsIsValid = false;
     m_shadowRootRareData->clearDescendantInsertionPoints();
 }
 
 const HeapVector<Member<InsertionPoint>>& ShadowRoot::descendantInsertionPoints()
 {
-    DEFINE_STATIC_LOCAL(PersistentHeapVector<Member<InsertionPoint>>, emptyList, ());
+    DEFINE_STATIC_LOCAL(HeapVector<Member<InsertionPoint>>, emptyList, (new HeapVector<Member<InsertionPoint>>));
     if (m_shadowRootRareData && m_descendantInsertionPointsIsValid)
         return m_shadowRootRareData->descendantInsertionPoints();
 
     m_descendantInsertionPointsIsValid = true;
 
     if (!containsInsertionPoints())
         return emptyList;
 
     HeapVector<Member<InsertionPoint>> insertionPoints;
     for (InsertionPoint& insertionPoint : Traversal<InsertionPoint>::descendantsOf(*this))
@@ skipping 31 matching lines @@
     m_shadowRootRareData->clearDescendantSlots();
 }
 
 unsigned ShadowRoot::descendantSlotCount() const
 {
     return m_shadowRootRareData ? m_shadowRootRareData->descendantSlotCount() : 0;
 }
 
 const HeapVector<Member<HTMLSlotElement>>& ShadowRoot::descendantSlots()
 {
-    DEFINE_STATIC_LOCAL(PersistentHeapVector<Member<HTMLSlotElement>>, emptyList, ());
+    DEFINE_STATIC_LOCAL(HeapVector<Member<HTMLSlotElement>>, emptyList, (new HeapVector<Member<HTMLSlotElement>>));
     if (m_descendantSlotsIsValid) {
         ASSERT(m_shadowRootRareData);
         return m_shadowRootRareData->descendantSlots();
     }
     if (descendantSlotCount() == 0)
         return emptyList;
 
     ASSERT(m_shadowRootRareData);
     HeapVector<Member<HTMLSlotElement>> slots;
     slots.reserveCapacity(descendantSlotCount());
     for (HTMLSlotElement& slot : Traversal<HTMLSlotElement>::descendantsOf(rootNode()))
         slots.append(&slot);
     m_shadowRootRareData->setDescendantSlots(slots);
     m_descendantSlotsIsValid = true;
     return m_shadowRootRareData->descendantSlots();
 }
 
 DEFINE_TRACE(ShadowRoot)
 {
     visitor->trace(m_prev);
     visitor->trace(m_next);
     visitor->trace(m_shadowRootRareData);
     TreeScope::trace(visitor);
     DocumentFragment::trace(visitor);
 }
 
 } // namespace blink