compositor-worker: Introduce CompositorWorker.

Source/modules/compositorworker/CompositorWorkerMessagingProxy.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 CompositorWorkerMessagingProxy_h
+#define CompositorWorkerMessagingProxy_h
+
+#include "core/workers/WorkerMessagingProxy.h"
+
+namespace blink {
+
+class CompositorWorkerMessagingProxy final : public WorkerMessagingProxy {
+public:
+    CompositorWorkerMessagingProxy(Worker*, PassOwnPtrWillBeRawPtr<WorkerClients>);
+
+protected:
+    virtual ~CompositorWorkerMessagingProxy();
+
+    virtual PassRefPtr<WorkerThread> createWorkerThread(double originTime, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>);
+};
+
+} // namespace blink
+
+#endif // CompositorWorkerMessagingProxy_h