Introduce WorkletGlobalScopeProxy interface.

third_party/WebKit/Source/modules/compositorworker/CompositorWorkletThread.h

+// Copyright 2016 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 CompositorWorkletThread_h
+#define CompositorWorkletThread_h
+
+#include "modules/worklet/WorkletThread.h"
+#include "wtf/PassOwnPtr.h"
+
+namespace blink {
+
+class CompositorWorkletThread final : public WorkletThread {
+public:
+    static PassOwnPtr<CompositorWorkletThread> create(const KURL&, const String& userAgent, PassRefPtr<SecurityOrigin>);
+    ~CompositorWorkletThread() override;
+
+    WorkerBackingThread& workerBackingThread() final;
+
+protected:
+    WorkletGlobalScope* createWorkletGlobalScope(const KURL&, const String& userAgent, PassRefPtr<SecurityOrigin>) final;
+
+private:
+    CompositorWorkletThread();
+};
+
+} // namespace blink
+
+#endif // CompositorWorkletThread_h