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

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 00c8ca2d67c0f489f10c7ad4862100d0f336bb41..7378b3d349abf57907fa7af6964f47cac57ddc63 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -149,9 +149,10 @@
 #include "public/web/WebSelection.h"
 #include "public/web/WebViewClient.h"
 #include "public/web/WebWindowFeatures.h"
+#include "web/AnimationWorkletProxyClientImpl.h"
 #include "web/CompositionUnderlineVectorBuilder.h"
 #include "web/CompositorMutatorImpl.h"
-#include "web/CompositorProxyClientImpl.h"
+#include "web/CompositorWorkerProxyClientImpl.h"
 #include "web/ContextFeaturesClientImpl.h"
 #include "web/ContextMenuAllowedScope.h"
 #include "web/DatabaseClientImpl.h"
@@ -4153,14 +4154,24 @@ void WebViewImpl::forceNextDrawingBufferCreationToFail() {
   DrawingBuffer::forceNextDrawingBufferCreationToFail();
 }
 
-CompositorProxyClient* WebViewImpl::createCompositorProxyClient() {
+CompositorProxyClient* WebViewImpl::createCompositorProxyClient(
+    CompositorProxyClient::Type type) {
   if (!m_mutator) {
     std::unique_ptr<CompositorMutatorClient> mutatorClient =
         CompositorMutatorImpl::createClient();
     m_mutator = static_cast<CompositorMutatorImpl*>(mutatorClient->mutator());
     m_layerTreeView->setMutatorClient(std::move(mutatorClient));
   }
-  return new CompositorProxyClientImpl(m_mutator);
+
+  switch (type) {
+    case CompositorProxyClient::kWorkerClient:
+      return new CompositorWorkerProxyClientImpl(m_mutator);
+    case CompositorProxyClient::kWorkletClient:
+      return new AnimationWorkletProxyClientImpl(m_mutator);
+  }
+
+  NOTREACHED() << "Unexpected CompositorProxyClient::Type: " << type;
+  return nullptr;
 }
 
 void WebViewImpl::updatePageOverlays() {