[ServiceWorker] Update .focus() to return a WindowClient instead of bool.

Source/web/ServiceWorkerGlobalScopeClientImpl.cpp

 /*
  * Copyright (C) 2014 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 110 matching lines @@
 void ServiceWorkerGlobalScopeClientImpl::claim(WebServiceWorkerClientsClaimCallbacks* callbacks)
 {
     m_client.claim(callbacks);
 }
 
 void ServiceWorkerGlobalScopeClientImpl::focus(int clientID, WebServiceWorkerClientFocusCallback* callback)
 {
     m_client.focus(clientID, callback);
 }
 
+void ServiceWorkerGlobalScopeClientImpl::focus(int clientID, WebServiceWorkerClientCallbacks* callback)
+{
+    m_client.focus(clientID, callback);
+}
+
 ServiceWorkerGlobalScopeClientImpl::ServiceWorkerGlobalScopeClientImpl(WebServiceWorkerContextClient& client)
     : m_client(client)
 {
 }
 
 } // namespace blink