Refactor the Heap into ThreadHeap to prepare for per thread heaps

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

 // Copyright 2015 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 PersistentNode_h
 #define PersistentNode_h
 
 #include "platform/PlatformExport.h"
 #include "platform/heap/ThreadState.h"
 #include "wtf/Assertions.h"
@@ skipping 170 matching lines @@
     void prepareForThreadStateTermination(ThreadState*);
 
 private:
     // We don't make CrossThreadPersistentRegion inherit from PersistentRegion
     // because we don't want to virtualize performance-sensitive methods
     // such as PersistentRegion::allocate/freePersistentNode.
     OwnPtr<PersistentRegion> m_persistentRegion;
     Mutex m_mutex;
 };
 
+class XThreadPersistentRegion final {

[haraken, 2016/01/07 08:06:22]

XThreadPersistentRegion and CrossThreadPersistentRegion is the same thing,
right? Would typedef be enough?

+public:
+    XThreadPersistentRegion() : m_persistentRegion(adoptPtr(new PersistentRegion)) { }
+
+    PersistentNode* allocatePersistentNode(void* self, TraceCallback trace)
+    {
+        MutexLocker lock(m_mutex);
+        return m_persistentRegion->allocatePersistentNode(self, trace);
+    }
+
+    void freePersistentNode(PersistentNode* persistentNode)
+    {
+        MutexLocker lock(m_mutex);
+        m_persistentRegion->freePersistentNode(persistentNode);
+    }
+
+    void tracePersistentNodes(Visitor* visitor)
+    {
+        MutexLocker lock(m_mutex);
+        m_persistentRegion->tracePersistentNodes(visitor);
+    }
+
+    void prepareForThreadStateTermination(ThreadState*);
+
+private:
+    // We don't make CrossThreadPersistentRegion inherit from PersistentRegion
+    // because we don't want to virtualize performance-sensitive methods
+    // such as PersistentRegion::allocate/freePersistentNode.
+    OwnPtr<PersistentRegion> m_persistentRegion;
+    Mutex m_mutex;
+};
+
 } // namespace blink
 
 #endif