ServiceWorker: Keep the worker alive until FetchEvent.waitUntil settles

content/browser/service_worker/service_worker_metrics.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_METRICS_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
@@ skipping 77 matching lines @@
     // GEOFENCING = 6,  // Obsolete
     // SERVICE_PORT_CONNECT = 7,  // Obsolete
     MESSAGE = 8,
     NOTIFICATION_CLOSE = 9,
     FETCH_MAIN_FRAME = 10,
     FETCH_SUB_FRAME = 11,
     FETCH_SHARED_WORKER = 12,
     FETCH_SUB_RESOURCE = 13,
     UNKNOWN = 14,  // Used when event type is not known.
     FOREIGN_FETCH = 15,
+    FETCH_WAITUNTIL = 16,

[falken, 2016/06/09 19:28:48]

It's unfortunate that WAITUNTIL is not an "event" since this is an EventType.
Should this be RequestType? I'm not sure the naming is making sense.

[shimazu, 2016/06/10 10:26:49]

Yes, I know. Hmm, I don't have good name now. 
It's mostly used as "EventType". EventType is currently used for
StartRequest(WithCustomTimer) and RecordStartWorkerResult.
RecordStartWorker is called in StartWorker, RunAfterStartWorker,
DidEnsureLiveRegistrationForStartWorker, and I fell it's a bit odd for
StartWorker to get a RequestType because StartWorker itself doesn't request a
message sent back from the service worker.

[falken, 2016/06/16 06:23:09]

I don't think it's so odd, since StartWorker itself doesn't dispatch an event
either. But this enum is also not really exactly "request" since it also splits
up fetch into MAIN_FRAME, SUB_FRAME, etc. for UMA purposes.

Anyway, I think we can go ahead and just put a comment explaining what EventType
is and how it's mostly events but also requests, since events typically have a
1:1 correspondence with requests except for the fetch event.

[shimazu, 2016/06/21 02:43:37]

Done.

     // Add new events to record here.
     NUM_TYPES
   };
 
   // Used for UMA. Append only.
   enum class Site {
     OTHER,  // Obsolete
     NEW_TAB_PAGE,
     WITH_FETCH_HANDLER,
     WITHOUT_FETCH_HANDLER,
@@ skipping 123 matching lines @@
   static void RecordStartStatusAfterFailure(int failure_count,
                                             ServiceWorkerStatusCode status);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ServiceWorkerMetrics);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_METRICS_H_