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

third_party/WebKit/Source/core/page/ChromeClient.h

Index: third_party/WebKit/Source/core/page/ChromeClient.h
diff --git a/third_party/WebKit/Source/core/page/ChromeClient.h b/third_party/WebKit/Source/core/page/ChromeClient.h
index e1785e59c60e604a0a4f9e1958d2a0cc6f7816a0..5d4fc396fe7ece26afc70a10a4f008e672a97ac3 100644
--- a/third_party/WebKit/Source/core/page/ChromeClient.h
+++ b/third_party/WebKit/Source/core/page/ChromeClient.h
@@ -26,6 +26,7 @@
 #include "base/gtest_prod_util.h"
 #include "core/CoreExport.h"
 #include "core/dom/AXObjectCache.h"
+#include "core/dom/CompositorProxyClient.h"
 #include "core/inspector/ConsoleTypes.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/NavigationPolicy.h"
@@ -50,7 +51,6 @@ class AXObject;
 class ColorChooser;
 class ColorChooserClient;
 class CompositorAnimationTimeline;
-class CompositorProxyClient;
 class DateTimeChooser;
 class DateTimeChooserClient;
 class Element;
@@ -324,7 +324,9 @@ class CORE_EXPORT ChromeClient : public HostWindow {
   virtual void registerPopupOpeningObserver(PopupOpeningObserver*) = 0;
   virtual void unregisterPopupOpeningObserver(PopupOpeningObserver*) = 0;
 
-  virtual CompositorProxyClient* createCompositorProxyClient(LocalFrame*) = 0;
+  virtual CompositorProxyClient* createCompositorProxyClient(
+      CompositorProxyClient::Type,
+      LocalFrame*) = 0;
 
   virtual FloatSize elasticOverscroll() const { return FloatSize(); }