Introduce ServiceWorker.EventDispatchingDelay UMA

content/renderer/service_worker/service_worker_context_client.cc

Index: content/renderer/service_worker/service_worker_context_client.cc
diff --git a/content/renderer/service_worker/service_worker_context_client.cc b/content/renderer/service_worker/service_worker_context_client.cc
index fbb10ca91d78ee51388ac9f28cc718bf8ee3dd94..7498e1c70394ab31a937047bef4928c88464e456 100644
--- a/content/renderer/service_worker/service_worker_context_client.cc
+++ b/content/renderer/service_worker/service_worker_context_client.cc
@@ -510,15 +510,18 @@ void ServiceWorkerContextClient::didHandleInstallEvent(
       GetRoutingID(), request_id, result, proxy_->hasFetchEventHandler()));
 }
 
-void ServiceWorkerContextClient::respondToFetchEvent(int response_id) {
+void ServiceWorkerContextClient::respondToFetchEvent(
+    int response_id,
+    double event_dispatch_time) {
   Send(new ServiceWorkerHostMsg_FetchEventResponse(
       GetRoutingID(), response_id, SERVICE_WORKER_FETCH_EVENT_RESULT_FALLBACK,
-      ServiceWorkerResponse()));
+      ServiceWorkerResponse(), base::Time::FromDoubleT(event_dispatch_time)));
 }
 
 void ServiceWorkerContextClient::respondToFetchEvent(
     int response_id,
-    const blink::WebServiceWorkerResponse& web_response) {
+    const blink::WebServiceWorkerResponse& web_response,
+    double event_dispatch_time) {
   ServiceWorkerHeaderMap headers;
   GetServiceWorkerHeaderMapFromWebResponse(web_response, &headers);
   ServiceWorkerHeaderList cors_exposed_header_names;
@@ -534,7 +537,7 @@ void ServiceWorkerContextClient::respondToFetchEvent(
       web_response.cacheStorageCacheName().utf8(), cors_exposed_header_names);
   Send(new ServiceWorkerHostMsg_FetchEventResponse(
       GetRoutingID(), response_id, SERVICE_WORKER_FETCH_EVENT_RESULT_RESPONSE,
-      response));
+      response, base::Time::FromDoubleT(event_dispatch_time)));
 }
 
 void ServiceWorkerContextClient::didHandleFetchEvent(