Reset ThreadState weak callback stack before GCing.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CallbackStack_h
 #define CallbackStack_h
 
 #include "platform/heap/BlinkGC.h"
 #include "wtf/Allocator.h"
 #include "wtf/Assertions.h"
@@ skipping 49 matching lines @@
 private:
     class Block {
         USING_FAST_MALLOC(Block);
     public:
         Block(Block* next, size_t blockSize);
         ~Block();
 
 #if ENABLE(ASSERT)
         void clear();
 #endif
+        void reset();
         void decommit();
 
         Block* next() const { return m_next; }
         void setNext(Block* next) { m_next = next; }
 
         bool isEmptyBlock() const
         {
             return m_current == &(m_buffer[0]);
         }
 
@@ skipping 51 matching lines @@
     Item* item = m_first->pop();
     if (LIKELY(!!item))
         return item;
 
     return popSlow();
 }
 
 } // namespace blink
 
 #endif // CallbackStack_h