[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

third_party/WebKit/Source/modules/compositorworker/AnimationWorkletMessagingProxy.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 AnimationWorkletMessagingProxy_h
+#define AnimationWorkletMessagingProxy_h
+
+#include "core/workers/ThreadedWorkletMessagingProxy.h"
+#include "wtf/Allocator.h"
+#include <memory>
+
+namespace blink {
+
+class ExecutionContext;
+class WorkerThread;
+
+class AnimationWorkletMessagingProxy final : public ThreadedWorkletMessagingProxy {
+    USING_FAST_MALLOC(AnimationWorkletMessagingProxy);
+public:
+    explicit AnimationWorkletMessagingProxy(ExecutionContext*);
+
+protected:
+    ~AnimationWorkletMessagingProxy() override;
+
+    std::unique_ptr<WorkerThread> createWorkerThread(double originTime) override;
+};
+
+} // namespace blink
+
+#endif // AnimationWorkletMessagingProxy_h