Add UMA to record the ratio of how many fetch events are not handled

content/browser/service_worker/service_worker_version.h

 // 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.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_
 
 #include <map>
 #include <queue>
 #include <set>
@@ skipping 311 matching lines @@
                            ActivateWaitingVersion);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerVersionTest, IdleTimeout);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerVersionTest, SetDevToolsAttached);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerWaitForeverInFetchTest, RequestTimeout);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerFailToStartTest, Timeout);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerVersionBrowserTest,
                            TimeoutStartingWorker);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerVersionBrowserTest,
                            TimeoutWorkerInEvent);
 
+  class ServiceWorkerEventMetrics;
+
   typedef ServiceWorkerVersion self;
   using ServiceWorkerClients = std::vector<ServiceWorkerClientInfo>;
 
   enum RequestType {
     REQUEST_ACTIVATE,
     REQUEST_INSTALL,
     REQUEST_FETCH,
     REQUEST_SYNC,
     REQUEST_NOTIFICATION_CLICK,
     REQUEST_PUSH,
@@ skipping 204 matching lines @@
 
   std::vector<int> pending_skip_waiting_requests_;
   scoped_ptr<net::HttpResponseInfo> main_script_http_info_;
 
   // The status when StartWorker was invoked. Used for UMA.
   Status prestart_status_ = NEW;
   // If not OK, the reason that StartWorker failed. Used for
   // running |start_callbacks_|.
   ServiceWorkerStatusCode start_worker_status_ = SERVICE_WORKER_OK;
 
+  scoped_ptr<ServiceWorkerEventMetrics> metrics_;
+
   base::WeakPtrFactory<ServiceWorkerVersion> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerVersion);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_VERSION_H_