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 66b4ea068a595c666b9eeeb98090f4f84fb59eb6..7f53069b6b060f0860fbe6139fe2e78568a22f2d 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/AnimationWorkletProxyClient.h"
 #include "core/inspector/ConsoleTypes.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/NavigationPolicy.h"
@@ -49,8 +50,8 @@ namespace blink {
 class AXObject;
 class ColorChooser;
 class ColorChooserClient;
+class CompositorWorkerProxyClient;
 class CompositorAnimationTimeline;
-class CompositorProxyClient;
 class DateTimeChooser;
 class DateTimeChooserClient;
 class Element;
@@ -326,7 +327,10 @@ class CORE_EXPORT ChromeClient : public HostWindow {
   virtual void registerPopupOpeningObserver(PopupOpeningObserver*) = 0;
   virtual void unregisterPopupOpeningObserver(PopupOpeningObserver*) = 0;
 
-  virtual CompositorProxyClient* createCompositorProxyClient(LocalFrame*) = 0;
+  virtual CompositorWorkerProxyClient* createCompositorWorkerProxyClient(
+      LocalFrame*) = 0;
+  virtual AnimationWorkletProxyClient* createAnimationWorkletProxyClient(
+      LocalFrame*) = 0;
 
   virtual FloatSize elasticOverscroll() const { return FloatSize(); }