Oilpan: Introduce memory pool for CallbackStacks

third_party/WebKit/Source/platform/heap/ThreadState.h

 /*
  * 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:
  *
  *     * 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 633 matching lines @@
     size_t m_arenaAges[BlinkGC::NumberOfArenas];
     size_t m_currentArenaAges;
 
     bool m_perThreadHeapEnabled;
     bool m_isTerminating;
     GarbageCollectedMixinConstructorMarker* m_gcMixinMarker;
 
     bool m_shouldFlushHeapDoesNotContainCache;
     GCState m_gcState;
 
-    CallbackStack* m_threadLocalWeakCallbackStack;
+    std::unique_ptr<CallbackStack> m_threadLocalWeakCallbackStack;
 
     // Pre-finalizers are called in the reverse order in which they are
     // registered by the constructors (including constructors of Mixin objects)
     // for an object, by processing the m_orderedPreFinalizers back-to-front.
     ListHashSet<PreFinalizer> m_orderedPreFinalizers;
 
     v8::Isolate* m_isolate;
     void (*m_traceDOMWrappers)(v8::Isolate*, Visitor*);
     void (*m_invalidateDeadObjectsInWrappersMarkingDeque)(v8::Isolate*);
 
@@ skipping 41 matching lines @@
 
 template<> class ThreadStateFor<AnyThread> {
     STATIC_ONLY(ThreadStateFor);
 public:
     static ThreadState* state() { return ThreadState::current(); }
 };
 
 } // namespace blink
 
 #endif // ThreadState_h