WebServiceWorkerProxy instances can be unwrapped to ServiceWorkers.

Source/modules/serviceworkers/ServiceWorker.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 #include "bindings/v8/ScriptWrappable.h"
 #include "bindings/v8/SerializedScriptValue.h"
 #include "core/workers/AbstractWorker.h"
 #include "public/platform/WebServiceWorker.h"
 #include "public/platform/WebServiceWorkerProxy.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 
-namespace blink {
-class WebServiceWorker;
-}
-
 namespace WebCore {
 
 class ScriptState;
 class ScriptPromiseResolverWithContext;
 
 class ServiceWorker
     : public AbstractWorker
     , public ScriptWrappable
     , public blink::WebServiceWorkerProxy {
 public:
     static PassRefPtr<ServiceWorker> create(ExecutionContext*, PassOwnPtr<blink::WebServiceWorker>);
 
     virtual ~ServiceWorker() { }
 
     // For CallbackPromiseAdapter
     typedef blink::WebServiceWorker WebType;
     static PassRefPtr<ServiceWorker> from(ScriptPromiseResolverWithContext*, WebType* worker);
 
+    static PassRefPtr<ServiceWorker> from(ScriptState*, WebType*);
+
     void postMessage(PassRefPtr<SerializedScriptValue> message, const MessagePortArray*, ExceptionState&);
 
     String scope() const;
     String url() const;
     const AtomicString& state() const;
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
 
     // WebServiceWorkerProxy overrides.
     virtual bool isReady() OVERRIDE;
     virtual void dispatchStateChangeEvent() OVERRIDE;
 
     // AbstractWorker overrides.
     virtual const AtomicString& interfaceName() const OVERRIDE;
 
 private:
     class ThenFunction;
 
     ServiceWorker(ExecutionContext*, PassOwnPtr<blink::WebServiceWorker>);
     void onPromiseResolved();
     void waitOnPromise(ScriptPromise);
 
     OwnPtr<blink::WebServiceWorker> m_outerWorker;
     bool m_isPromisePending;
 };
 
 } // namespace WebCore
 
 #endif // ServiceWorker_h