[NOT READY FOR REVIEW YET]workers: Some refactoring to allow creating new kind of worker threads

Source/core/workers/Worker.h

 /*
  * Copyright (C) 2008, 2010 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 38 matching lines @@
 class Worker final : public AbstractWorker, private WorkerScriptLoaderClient {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<Worker> create(ExecutionContext*, const String& url, ExceptionState&);
     virtual ~Worker();
 
     virtual const AtomicString& interfaceName() const override;
 
     void postMessage(ExecutionContext*, PassRefPtr<SerializedScriptValue> message, const MessagePortArray*, ExceptionState&);
 
+    bool initialize(ExecutionContext*, const String&, ExceptionState&);
     void terminate();
 
     virtual void stop() override;
     virtual bool hasPendingActivity() const override;
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(message);
 
     virtual void trace(Visitor*) override;
 
 private:
     explicit Worker(ExecutionContext*);
 
     // WorkerScriptLoaderClient callbacks
     virtual void didReceiveResponse(unsigned long identifier, const ResourceResponse&) override;
     virtual void notifyFinished() override;
 
     RefPtr<WorkerScriptLoader> m_scriptLoader;
     WorkerGlobalScopeProxy* m_contextProxy; // The proxy outlives the worker to perform thread shutdown.
 };
 
 } // namespace blink
 
 #endif // Worker_h