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

content/browser/service_worker/service_worker_url_request_job.cc

Index: content/browser/service_worker/service_worker_url_request_job.cc
diff --git a/content/browser/service_worker/service_worker_url_request_job.cc b/content/browser/service_worker/service_worker_url_request_job.cc
index 6a795d630de276a655d8a46490ff576385bed64f..cc10f3ee4cb4cdde65a7663551858b7c8088a78d 100644
--- a/content/browser/service_worker/service_worker_url_request_job.cc
+++ b/content/browser/service_worker/service_worker_url_request_job.cc
@@ -229,6 +229,8 @@ void ServiceWorkerURLRequestJob::StartRequest() {
       fetch_dispatcher_.reset(new ServiceWorkerFetchDispatcher(
           CreateFetchRequest(),
           provider_host_->active_version(),
+          base::Bind(&ServiceWorkerURLRequestJob::DidPrepareFetchEvent,
+                     weak_factory_.GetWeakPtr()),
           base::Bind(&ServiceWorkerURLRequestJob::DidDispatchFetchEvent,
                      weak_factory_.GetWeakPtr())));
       fetch_dispatcher_->Run();
@@ -322,6 +324,9 @@ bool ServiceWorkerURLRequestJob::CreateRequestBodyBlob(std::string* blob_uuid,
   return true;
 }
 
+void ServiceWorkerURLRequestJob::DidPrepareFetchEvent() {

[nhiroki, 2014/08/22 04:50:58]

Can you add a comment here?

For example, if you will implement this function in a subsequent CL, you can
add...

  // TODO(shimazu): Implement this (http://crbug.com/XXXXXX).

Or, if you want to do nothing here, you can add...

  // Nothing to do.

In general, an empty body would say nothing about an implementer's intention and
a sourcecode reader cannot figure out whether the implementer just forgot to
make it or not.

[horo, 2014/08/22 05:11:51]

Please write TODO comments.

[shimazu, 2014/08/25 02:17:40]

Done.

[shimazu, 2014/08/25 02:17:40]

Done.

+}
+
 void ServiceWorkerURLRequestJob::DidDispatchFetchEvent(
     ServiceWorkerStatusCode status,
     ServiceWorkerFetchEventResult fetch_result,