Introduce AnimationWorkletProxyClient and necessary plumbing to get it in worklet messaging proxy.

third_party/WebKit/Source/web/CompositorProxyClientFactoryImpl.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 CompositorProxyClientFactoryImpl_h
+#define CompositorProxyClientFactoryImpl_h
+
+#include "core/dom/CompositorProxyClientFactory.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class CompositorMutatorImpl;
+
+class CompositorProxyClientFactoryImpl final
+    : public GarbageCollectedFinalized<CompositorProxyClientFactoryImpl>,
+      public CompositorProxyClientFactory {
+ public:
+  CompositorProxyClientFactoryImpl(CompositorMutatorImpl*);

[nhiroki, 2016/11/24 06:59:00]

explicit

[majidvp, 2016/11/28 14:43:21]

Done.

+  CompositorProxyClient* create(CompositorProxyClient::Type) override;
+
+  DEFINE_INLINE_TRACE() {}
+
+ private:
+  CrossThreadPersistent<CompositorMutatorImpl> m_mutator;
+};
+
+}  // namespace blink
+
+#endif  // CompositorProxyClientFactoryImpl_h