ServiceWorker: Add UMA to measure execution times of oninstall/onfetch

content/browser/service_worker/service_worker_metrics.cc

 // 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.
 
 #include "content/browser/service_worker/service_worker_metrics.h"
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics_action.h"
 #include "content/public/browser/user_metrics.h"
 
@@ skipping 37 matching lines @@
     ServiceWorkerDatabase::Status status) {
   UMA_HISTOGRAM_ENUMERATION("ServiceWorker.Database.WriteResult",
                             status, ServiceWorkerDatabase::STATUS_ERROR_MAX);
 }
 
 // static
 void ServiceWorkerMetrics::CountControlledPageLoad() {
   RecordAction(base::UserMetricsAction("ServiceWorker.ControlledPageLoad"));
 }
 
+// static
+void
+ServiceWorkerMetrics::MeasureFetchEventExecutionTime(base::TimeDelta delta) {

[nhiroki, 2014/09/26 07:28:17]

nit: Wrapping at the argument would be more common in our codebase.

Can you use const-ref for the argument?

+  UMA_HISTOGRAM_TIMES("ServiceWorker.FetchEventExecutionTime", delta);
+}
+
+// static
+void
+ServiceWorkerMetrics::MeasureRegistrationTime(base::TimeDelta delta) {

[nhiroki, 2014/09/26 07:28:17]

ditto.

+  UMA_HISTOGRAM_TIMES("ServiceWorker.RegistrationTime", delta);
+}
+
 }  // namespace content