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

third_party/WebKit/Source/web/CompositorProxyClientImpl.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 CompositorProxyClientImpl_h
-#define CompositorProxyClientImpl_h
-
-#include "core/dom/CompositorProxyClient.h"
-#include "platform/heap/Handle.h"
-#include "wtf/Noncopyable.h"
-
-namespace blink {
-
-class CompositorMutableStateProvider;
-class CompositorMutatorImpl;
-class CompositorWorkerGlobalScope;
-class WorkerGlobalScope;
-
-// Mediates between one CompositorWorkerGlobalScope and the associated
-// CompositorMutatorImpl.  There is one CompositorProxyClientImpl per worker
-// but there may be multiple for a given mutator, e.g. if a single document
-// creates multiple CompositorWorker objects.
-//
-// Should be accessed only on the compositor thread.
-class CompositorProxyClientImpl final
-    : public GarbageCollectedFinalized<CompositorProxyClientImpl>,
-      public CompositorProxyClient {
-  USING_GARBAGE_COLLECTED_MIXIN(CompositorProxyClientImpl);
-  WTF_MAKE_NONCOPYABLE(CompositorProxyClientImpl);
-
- public:
-  CompositorProxyClientImpl(CompositorMutatorImpl*);
-  DECLARE_VIRTUAL_TRACE();
-
-  // Runs the animation frame callback for the frame starting at the given time.
-  // Returns true if another animation frame was requested (i.e. should be
-  // reinvoked next frame).
-  bool mutate(double monotonicTimeNow, CompositorMutableStateProvider*);
-
-  // CompositorProxyClient:
-  void dispose() override;
-  void setGlobalScope(WorkerGlobalScope*) override;
-  void requestAnimationFrame() override;
-  void registerCompositorProxy(CompositorProxy*) override;
-  void unregisterCompositorProxy(CompositorProxy*) override;
-
- private:
-  bool executeAnimationFrameCallbacks(double monotonicTimeNow);
-
-  CrossThreadPersistent<CompositorMutatorImpl> m_mutator;
-
-  CrossThreadPersistent<CompositorWorkerGlobalScope> m_globalScope;
-  bool m_requestedAnimationFrameCallbacks;
-
-  HeapHashSet<WeakMember<CompositorProxy>> m_proxies;
-};
-
-}  // namespace blink
-
-#endif  // CompositorProxyClientImpl_h