ServiceWorker: Make a way to retrieve a service worker version id (Blink)

Source/core/loader/EmptyClients.h

 /*
  * Copyright (C) 2006 Eric Seidel (eric@webkit.org)
  * Copyright (C) 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. 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
@@ skipping 230 matching lines @@
     virtual void didCreateScriptContext(v8::Handle<v8::Context>, int extensionGroup, int worldId) override { }
     virtual void willReleaseScriptContext(v8::Handle<v8::Context>, int worldId) override { }
     virtual bool allowScriptExtension(const String& extensionName, int extensionGroup, int worldId) override { return false; }
 
     virtual blink::WebCookieJar* cookieJar() const override { return 0; }
 
     virtual void didRequestAutocomplete(HTMLFormElement*) override;
 
     virtual PassOwnPtr<blink::WebServiceWorkerProvider> createServiceWorkerProvider() override;
     virtual bool isControlledByServiceWorker(DocumentLoader&) override { return false; }
+    virtual int64_t serviceWorkerID(DocumentLoader&) override { return -1; }
     virtual PassOwnPtr<blink::WebApplicationCacheHost> createApplicationCacheHost(blink::WebApplicationCacheHostClient*) override;
 };
 
 class EmptyTextCheckerClient : public TextCheckerClient {
 public:
     ~EmptyTextCheckerClient() { }
 
     virtual bool shouldEraseMarkersAfterChangeSelection(TextCheckingType) const override { return true; }
     virtual void checkSpellingOfString(const String&, int*, int*) override { }
     virtual String getAutoCorrectSuggestionForMisspelledWord(const String&) override { return String(); }
@@ skipping 75 matching lines @@
 public:
     virtual PassOwnPtr<StorageNamespace> createSessionStorageNamespace() override;
     virtual bool canAccessStorage(LocalFrame*, StorageType) const override { return false; }
 };
 
 void fillWithEmptyClients(Page::PageClients&);
 
 }
 
 #endif // EmptyClients_h