Add UMA for how long service workers run for.

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 aa0aa0862133853c59e79b0674dfe8427ddb54a9..ab94115d23c36f0ebed703b573547cdb1d79ccbb 100644
--- a/content/browser/service_worker/service_worker_metrics.cc
+++ b/content/browser/service_worker/service_worker_metrics.cc
@@ -978,4 +978,12 @@ void ServiceWorkerMetrics::RecordContextRequestHandlerStatus(
   }
 }
 
+void ServiceWorkerMetrics::RecordRuntime(base::TimeDelta time) {
+  UMA_HISTOGRAM_LONG_TIMES("ServiceWorker.Runtime", time);
+}
+
+void ServiceWorkerMetrics::RecordStillRunning(base::TimeDelta time) {
+  UMA_HISTOGRAM_LONG_TIMES("ServiceWorker.StillRunningTime", time);
+}
+
 }  // namespace content