ServiceWorker: Insert TRACE_EVENT to watch a breakdown of the ServiceWorker's performance on chome:…

content/browser/service_worker/service_worker_fetch_dispatcher.cc

Index: content/browser/service_worker/service_worker_fetch_dispatcher.cc
diff --git a/content/browser/service_worker/service_worker_fetch_dispatcher.cc b/content/browser/service_worker/service_worker_fetch_dispatcher.cc
index c5c1d0200da20f24d3cffc00d70c46f16baf883a..7ed3051e3f12ea899454fc69f7a2a5134a72a566 100644
--- a/content/browser/service_worker/service_worker_fetch_dispatcher.cc
+++ b/content/browser/service_worker/service_worker_fetch_dispatcher.cc
@@ -5,6 +5,7 @@
 #include "content/browser/service_worker/service_worker_fetch_dispatcher.h"
 
 #include "base/bind.h"
+#include "base/debug/trace_event.h"
 #include "content/browser/service_worker/service_worker_version.h"
 
 namespace content {
@@ -57,6 +58,10 @@ void ServiceWorkerFetchDispatcher::DidFailActivation() {
 }
 
 void ServiceWorkerFetchDispatcher::DispatchFetchEvent() {
+  TRACE_EVENT_ASYNC_BEGIN0(
+      "ServiceWorker",
+      "ServiceWorkerFetchDispatcher::DispatchFetchEvent",
+      request_.get());
   version_->DispatchFetchEvent(
       *request_.get(),
       base::Bind(&ServiceWorkerFetchDispatcher::DidPrepare,
@@ -75,6 +80,10 @@ void ServiceWorkerFetchDispatcher::DidFinish(
     ServiceWorkerStatusCode status,
     ServiceWorkerFetchEventResult fetch_result,
     const ServiceWorkerResponse& response) {
+  TRACE_EVENT_ASYNC_END0(
+      "ServiceWorker",
+      "ServiceWorkerFetchDispatcher::DispatchFetchEvent",
+      request_.get());
   DCHECK(!fetch_callback_.is_null());
   FetchCallback fetch_callback = fetch_callback_;
   fetch_callback.Run(status, fetch_result, response);