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 4fd3c4068ab5c028d8e9844ebc6f5d0d43f8f29a..6f58e3a918f6be2d76e692fca06ed803fc2ba861 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -151,7 +151,6 @@
 #include "public/web/WebWindowFeatures.h"
 #include "web/CompositionUnderlineVectorBuilder.h"
 #include "web/CompositorMutatorImpl.h"
-#include "web/CompositorProxyClientImpl.h"
 #include "web/ContextFeaturesClientImpl.h"
 #include "web/ContextMenuAllowedScope.h"
 #include "web/DatabaseClientImpl.h"
@@ -384,6 +383,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client,
       m_displayMode(WebDisplayModeBrowser),
       m_elasticOverscroll(FloatSize()),
       m_mutator(nullptr),
+      m_proxyClientFactory(nullptr),
       m_scheduler(wrapUnique(Platform::current()
                                  ->currentThread()
                                  ->scheduler()
@@ -2522,6 +2522,7 @@ void WebViewImpl::willCloseLayerTreeView() {
   setRootLayer(nullptr);
 
   m_mutator = nullptr;
+  m_proxyClientFactory = nullptr;
   m_layerTreeView = nullptr;
 }
 
@@ -4158,14 +4159,15 @@ void WebViewImpl::forceNextDrawingBufferCreationToFail() {
   DrawingBuffer::forceNextDrawingBufferCreationToFail();
 }
 
-CompositorProxyClient* WebViewImpl::createCompositorProxyClient() {
-  if (!m_mutator) {
+CompositorProxyClientFactory* WebViewImpl::compositorProxyClientFactory() {
+  if (!m_proxyClientFactory) {
     std::unique_ptr<CompositorMutatorClient> mutatorClient =
         CompositorMutatorImpl::createClient();
     m_mutator = static_cast<CompositorMutatorImpl*>(mutatorClient->mutator());
     m_layerTreeView->setMutatorClient(std::move(mutatorClient));
+    m_proxyClientFactory = new CompositorProxyClientFactoryImpl(m_mutator);
   }
-  return new CompositorProxyClientImpl(m_mutator);
+  return m_proxyClientFactory;
 }
 
 void WebViewImpl::updatePageOverlays() {