[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h

Index: third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h
diff --git a/third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h b/third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h
index c77fd8fe5ecdcdd55ad5dedacdb75c5382f31b4a..cbb75791952925d26fd7c3fefa697f9f285a3c2a 100644
--- a/third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h
+++ b/third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.h
@@ -12,7 +12,7 @@
 namespace blink {
 
 class LocalFrame;
-class ThreadedWorkletGlobalScopeProxy;
+class ThreadedWorkletMessagingProxy;
 class WorkletGlobalScopeProxy;
 
 class MODULES_EXPORT AnimationWorklet final : public Worklet {
@@ -28,8 +28,9 @@ public:
 private:
     explicit AnimationWorklet(LocalFrame*);
 
-    // TODO(ikilpatrick): this will change to a raw ptr once we have a thread.
-    std::unique_ptr<ThreadedWorkletGlobalScopeProxy> m_workletGlobalScopeProxy;
+    // The proxy outlives the worklet as it is used to perform thread shutdown,
+    // it deletes itself once this has occured.
+    ThreadedWorkletMessagingProxy* const m_workletMessagingProxy;
 };
 
 } // namespace blink