Oilpan: Reduce the reserved size of CallbackStacks

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/ThreadState.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;
     };
 
-    CallbackStack();
+    explicit CallbackStack(size_t);
     ~CallbackStack();
 
     void clear();
 
     Item* allocateEntry();
     Item* pop();
 
     bool isEmpty() const;
 
     void invokeEphemeronCallbacks(Visitor*);
 
 #if ENABLE(ASSERT)
     bool hasCallbackForObject(const void*);
 #endif
 
 private:
-    static const size_t blockSize = 8192;
-
     class Block {
         USING_FAST_MALLOC(Block);
     public:
-        explicit Block(Block* next)
-            : m_limit(&(m_buffer[blockSize]))
-            , m_current(&(m_buffer[0]))
-            , m_next(next)
-        {
-            clearUnused();
-        }
-
-        ~Block()
-        {
-            clearUnused();
-        }
+        explicit Block(Block*, size_t);
+        ~Block();
 
         void clear();
 
         Block* next() const { return m_next; }
         void setNext(Block* next) { m_next = next; }
+        size_t blockSize() const { return m_blockSize; }
 
         bool isEmptyBlock() const
         {
             return m_current == &(m_buffer[0]);
         }
 
-        size_t size() const
-        {
-            return blockSize - (m_limit - m_current);
-        }
-
         Item* allocateEntry()
         {
             if (LIKELY(m_current < m_limit))
                 return m_current++;
             return nullptr;
         }
 
         Item* pop()
         {
             if (UNLIKELY(isEmptyBlock()))
                 return nullptr;
             return --m_current;
         }
 
         void invokeEphemeronCallbacks(Visitor*);
 #if ENABLE(ASSERT)
         bool hasCallbackForObject(const void*);
 #endif
 
     private:
         void clearUnused();
 
-        Item m_buffer[blockSize];
+        Item* m_buffer;
         Item* m_limit;
         Item* m_current;
         Block* m_next;
+        size_t m_blockSize;
     };
 
     Item* popSlow();
     Item* allocateEntrySlow();
     void invokeOldestCallbacks(Block*, Block*, Visitor*);
     bool hasJustOneBlock() const;
 
     Block* m_first;
     Block* m_last;
 };
@@ skipping 12 matching lines @@
     Item* item = m_first->pop();
     if (LIKELY(!!item))
         return item;
 
     return popSlow();
 }
 
 } // namespace blink
 
 #endif // CallbackStack_h