compositor-worker: Introduce CompositorWorker.

Source/core/workers/WorkerThread.h

Index: Source/core/workers/WorkerThread.h
diff --git a/Source/core/workers/WorkerThread.h b/Source/core/workers/WorkerThread.h
index 9c0c364bcf35b989b7499dbce5ccf6721015987f..83e4b2885271beb7fe017952b473fca2a0ebce2b 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -65,8 +65,9 @@ public:
     virtual void start();
     virtual void stop();
 
-    void didStartRunLoop();
-    void didStopRunLoop();
+    virtual PassOwnPtr<WebThreadSupportingGC> createWebThreadSupportingGC();
+    virtual void didStartRunLoop();
+    virtual void didStopRunLoop();
 
     v8::Isolate* isolate() const { return m_isolate; }
 
@@ -117,6 +118,11 @@ protected:
 
     virtual void postInitialize() { }
 
+    virtual v8::Isolate* initializeIsolate();
+    virtual void willDestroyIsolate();
+    virtual void destroyIsolate();
+    virtual void terminateV8Execution();
+
 private:
     friend class WorkerSharedTimer;
     friend class WorkerThreadShutdownFinishTask;
@@ -130,11 +136,6 @@ private:
     void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
-    v8::Isolate* initializeIsolate();
-    void willDestroyIsolate();
-    void destroyIsolate();
-    void terminateV8Execution();
-
     bool m_terminated;
     OwnPtr<WorkerSharedTimer> m_sharedTimer;
     MessageQueue<WorkerThreadTask> m_debuggerMessageQueue;