[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef AnimationWorklet_h
 #define AnimationWorklet_h
 
 #include "core/workers/Worklet.h"
 #include "modules/ModulesExport.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class LocalFrame;
-class ThreadedWorkletGlobalScopeProxy;
+class ThreadedWorkletMessagingProxy;
 class WorkletGlobalScopeProxy;
 
 class MODULES_EXPORT AnimationWorklet final : public Worklet {
     WTF_MAKE_NONCOPYABLE(AnimationWorklet);
 public:
     static AnimationWorklet* create(LocalFrame*);
     ~AnimationWorklet() override;
 
+    void initialize() final;
+    bool isInitialized() const final;
+
     WorkletGlobalScopeProxy* workletGlobalScopeProxy() const final;
 
     DECLARE_VIRTUAL_TRACE();
 
 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* m_workletMessagingProxy;
 };
 
 } // namespace blink
 
 #endif // AnimationWorklet_h