ServiceWorker: Confirm the liveness of the associated context before handling message

content/browser/service_worker/service_worker_provider_host.cc

 // Copyright 2013 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.
 
 #include "content/browser/service_worker/service_worker_provider_host.h"
 
 #include "base/stl_util.h"
 #include "content/browser/message_port_message_filter.h"
 #include "content/browser/service_worker/service_worker_context_core.h"
 #include "content/browser/service_worker/service_worker_context_request_handler.h"
@@ skipping 155 matching lines @@
   if (context_ && version) {
     scoped_ptr<ServiceWorkerHandle> handle =
         ServiceWorkerHandle::Create(context_, dispatcher_host_,
                                     kDocumentMainThreadId, version);
     info = handle->GetObjectInfo();
     dispatcher_host_->RegisterServiceWorkerHandle(handle.Pass());
   }
   return info;
 }
 
+bool ServiceWorkerProviderHost::IsContextAlive() {
+  return context_ != NULL;
+}
+
 }  // namespace content