ServiceWorker: Stop asynchronously creating response accessors to fix crash due to null context

content/browser/service_worker/service_worker_write_to_cache_job.cc

Index: content/browser/service_worker/service_worker_write_to_cache_job.cc
diff --git a/content/browser/service_worker/service_worker_write_to_cache_job.cc b/content/browser/service_worker/service_worker_write_to_cache_job.cc
index b5477ab9a0195958a0be000ce5961f312dd8f918..4608c6fe4beb035e165faab5b6e5154b9729889c 100644
--- a/content/browser/service_worker/service_worker_write_to_cache_job.cc
+++ b/content/browser/service_worker/service_worker_write_to_cache_job.cc
@@ -97,13 +97,9 @@ void ServiceWorkerWriteToCacheJob::StartAsync() {
     return;
   }
 
-  // These uses of Unretained are safe because this object is the sole owner of
-  // |cache_writer_|, which in turn is the sole user of these callbacks.
   cache_writer_.reset(new ServiceWorkerCacheWriter(
-      base::Bind(&ServiceWorkerWriteToCacheJob::CreateCacheResponseReader,
-                 base::Unretained(this)),
-      base::Bind(&ServiceWorkerWriteToCacheJob::CreateCacheResponseWriter,
-                 base::Unretained(this))));
+      CreateCacheResponseReader(), CreateCacheResponseReader(),
+      CreateCacheResponseWriter()));
   version_->script_cache_map()->NotifyStartedCaching(url_, resource_id_);
   did_notify_started_ = true;
   StartNetRequest();