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

third_party/WebKit/Source/web/WebFrameWidgetImpl.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 116 matching lines @@
   Frame* focusedCoreFrame() const;
 
   // Returns the currently focused Element or null if no element has focus.
   Element* focusedElement() const;
 
   PaintLayerCompositor* compositor() const;
 
   // WebFrameWidgetBase overrides:
   bool forSubframe() const override { return true; }
   void scheduleAnimation() override;
-  CompositorProxyClient* createCompositorProxyClient() override;
+  CompositorProxyClient* createCompositorProxyClient(
+      CompositorProxyClient::Type) override;
   WebWidgetClient* client() const override { return m_client; }
   void setRootGraphicsLayer(GraphicsLayer*) override;
   void setRootLayer(WebLayer*) override;
   WebLayerTreeView* getLayerTreeView() const override;
   CompositorAnimationHost* animationHost() const override;
   HitTestResult coreHitTestResultAt(const WebPoint&) override;
 
   // Exposed for the purpose of overriding device metrics.
   void sendResizeEventAndRepaint();
 
@@ skipping 90 matching lines @@
 
 DEFINE_TYPE_CASTS(WebFrameWidgetImpl,
                   WebFrameWidgetBase,
                   widget,
                   widget->forSubframe(),
                   widget.forSubframe());
 
 }  // namespace blink
 
 #endif