[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

third_party/WebKit/Source/core/workers/Worklet.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 Worklet_h
 #define Worklet_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "core/dom/ActiveDOMObject.h"
 #include "core/fetch/ScriptResource.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class LocalFrame;
 class ResourceFetcher;
 class WorkletGlobalScopeProxy;
 class WorkletScriptLoader;
 
 class CORE_EXPORT Worklet : public GarbageCollectedFinalized<Worklet>, public ScriptWrappable, public ActiveDOMObject {
     DEFINE_WRAPPERTYPEINFO();
     USING_GARBAGE_COLLECTED_MIXIN(Worklet);
     WTF_MAKE_NONCOPYABLE(Worklet);
 public:
+    virtual void initialize() {}
+    virtual bool isInitialized() const { return true; }
+
     virtual WorkletGlobalScopeProxy* workletGlobalScopeProxy() const = 0;
 
     // Worklet
     ScriptPromise import(ScriptState*, const String& url);
 
     void notifyFinished(WorkletScriptLoader*);
 
     // ActiveDOMObject
     void stop() final;
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     // The Worklet inherits the url and userAgent from the frame->document().
     explicit Worklet(LocalFrame*);
 
 private:
     ResourceFetcher* fetcher() const { return m_fetcher.get(); }
 
     Member<ResourceFetcher> m_fetcher;
     HeapHashSet<Member<WorkletScriptLoader>> m_scriptLoaders;
 };
 
 } // namespace blink
 
 #endif // Worklet_h