Reduce weak callback stack reservation for non-main threads.

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 19 matching lines @@
         }
         void* object() { return m_object; }
         VisitorCallback callback() { return m_callback; }
         void call(Visitor* visitor) { m_callback(visitor, m_object); }
 
     private:
         void* m_object;
         VisitorCallback m_callback;
     };
 
-    explicit CallbackStack(size_t blockSize = defaultBlockSize);
+    explicit CallbackStack(size_t blockSize = kDefaultBlockSize);
     ~CallbackStack();
 
     void clear();
     void decommit();
 
     Item* allocateEntry();
     Item* pop();
 
     bool isEmpty() const;
 
     void invokeEphemeronCallbacks(Visitor*);
 
 #if ENABLE(ASSERT)
     bool hasCallbackForObject(const void*);
 #endif
 
     static const size_t kMinimalBlockSize;
+    static const size_t kDefaultBlockSize = (1 << 13);
 
 private:
-    static const size_t defaultBlockSize = (1 << 13);
-
     class Block {
         USING_FAST_MALLOC(Block);
     public:
         Block(Block* next, size_t blockSize);
         ~Block();
 
 #if ENABLE(ASSERT)
         void clear();
 #endif
         void decommit();
@@ skipping 60 matching lines @@
     Item* item = m_first->pop();
     if (LIKELY(!!item))
         return item;
 
     return popSlow();
 }
 
 } // namespace blink
 
 #endif // CallbackStack_h