ServiceWorker: Add prepare_callback in DispatchFetchEvent to notify the end of SW preparation.

content/browser/service_worker/service_worker_fetch_dispatcher.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_FETCH_DISPATCHER_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_FETCH_DISPATCHER_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "content/common/service_worker/service_worker_status_code.h"
 #include "content/common/service_worker/service_worker_types.h"
 
 namespace content {
 
 class ServiceWorkerVersion;
 
 // A helper class to dispatch fetch event to a service worker.
 class ServiceWorkerFetchDispatcher {
  public:
   typedef base::Callback<void(ServiceWorkerStatusCode,
                               ServiceWorkerFetchEventResult,
                               const ServiceWorkerResponse&)> FetchCallback;
 
   ServiceWorkerFetchDispatcher(scoped_ptr<ServiceWorkerFetchRequest> request,
                                ServiceWorkerVersion* version,
-                               const FetchCallback& callback);
+                               const base::Closure& prepare_callback,
+                               const FetchCallback& fetch_callback);
   ~ServiceWorkerFetchDispatcher();
 
   // Dispatches a fetch event to the |version| given in ctor, and fires
   // |callback| (also given in ctor) when finishes.
   void Run();
 
  private:
   void DidWaitActivation();
   void DidFailActivation();
   void DispatchFetchEvent();
+  void DidPrepare();
   void DidFinish(ServiceWorkerStatusCode status,
                  ServiceWorkerFetchEventResult fetch_result,
                  const ServiceWorkerResponse& response);
 
   scoped_refptr<ServiceWorkerVersion> version_;
-  FetchCallback callback_;
+  base::Closure prepare_callback_;
+  FetchCallback fetch_callback_;
   scoped_ptr<ServiceWorkerFetchRequest> request_;
   base::WeakPtrFactory<ServiceWorkerFetchDispatcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerFetchDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_FETCH_DISPATCHER_H_