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

content/browser/service_worker/service_worker_metrics.cc

Index: content/browser/service_worker/service_worker_metrics.cc
diff --git a/content/browser/service_worker/service_worker_metrics.cc b/content/browser/service_worker/service_worker_metrics.cc
index 6e3ddf1d7aaded7762fd92449e45077a38047d8d..ad8909261befa6a65588aeec84612a592b81db62 100644
--- a/content/browser/service_worker/service_worker_metrics.cc
+++ b/content/browser/service_worker/service_worker_metrics.cc
@@ -55,4 +55,16 @@ 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