Add blink interface (and code) for setting navigator.serviceWorker.current

public/platform/WebServiceWorkerProviderClient.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 14 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebServiceWorkerProviderClient_h
 #define WebServiceWorkerProviderClient_h
 
 namespace blink {
+class WebServiceWorker;
 class WebString;
 
-// This class catches any errors that may originate on the browser
-// side and not via a DOM API call, such as errors that occur when
-// loading resources through the service worker.
+// This class provides interface for embedders to talk to
+// ServiceWorkerContainer.
 class WebServiceWorkerProviderClient {
 public:
-    // FIXME: replace this general error handler with more specific error handlers.
-    virtual void didFailToStart(const WebString& message) { }
+    virtual ~WebServiceWorkerProviderClient() { }
 
-    virtual ~WebServiceWorkerProviderClient() { }
+    // The callee will take ownership of the given WebServiceWorker object.
+    virtual void setCurrentServiceWorker(WebServiceWorker*) = 0;
 };
 
 };
 
 #endif // WebServiceWorkerProviderClient_h