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

third_party/WebKit/Source/web/ChromeClientImpl.cpp

Index: third_party/WebKit/Source/web/ChromeClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/ChromeClientImpl.cpp b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
index 617bc5e4a4da7982c3b25631ad4414ad4487db8d..d9c3c44041b58c8a129b5c303958ccbd8f8c6723 100644
--- a/third_party/WebKit/Source/web/ChromeClientImpl.cpp
+++ b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
@@ -1157,10 +1157,20 @@ void ChromeClientImpl::didUpdateBrowserControls() const {
   m_webView->didUpdateBrowserControls();
 }
 
-CompositorProxyClient* ChromeClientImpl::createCompositorProxyClient(
-    LocalFrame* frame) {
+CompositorWorkerProxyClient*
+ChromeClientImpl::createCompositorWorkerProxyClient(LocalFrame* frame) {
+  WebLocalFrameImpl* webFrame = WebLocalFrameImpl::fromFrame(frame);
+  return webFrame->localRoot()
+      ->frameWidget()
+      ->createCompositorWorkerProxyClient();
+}
+
+AnimationWorkletProxyClient*
+ChromeClientImpl::createAnimationWorkletProxyClient(LocalFrame* frame) {
   WebLocalFrameImpl* webFrame = WebLocalFrameImpl::fromFrame(frame);
-  return webFrame->localRoot()->frameWidget()->createCompositorProxyClient();
+  return webFrame->localRoot()
+      ->frameWidget()
+      ->createAnimationWorkletProxyClient();
 }
 
 void ChromeClientImpl::registerPopupOpeningObserver(