Adding instrumentation to locate the source of jankiness.

content/browser/service_worker/service_worker_url_request_job.cc

Index: content/browser/service_worker/service_worker_url_request_job.cc
diff --git a/content/browser/service_worker/service_worker_url_request_job.cc b/content/browser/service_worker/service_worker_url_request_job.cc
index 0e6ef2b98fcc4d56a5b57c9d06f530c1d3a26c36..fcf377bb17ab4f8650f5d0a9552fc6dff6fa23d5 100644
--- a/content/browser/service_worker/service_worker_url_request_job.cc
+++ b/content/browser/service_worker/service_worker_url_request_job.cc
@@ -10,6 +10,7 @@
 
 #include "base/bind.h"
 #include "base/guid.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/strings/stringprintf.h"
 #include "base/time/time.h"
 #include "content/browser/service_worker/service_worker_fetch_dispatcher.h"
@@ -176,6 +177,11 @@ void ServiceWorkerURLRequestJob::OnBeforeNetworkStart(net::URLRequest* request,
 }
 
 void ServiceWorkerURLRequestJob::OnResponseStarted(net::URLRequest* request) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 ServiceWorkerURLRequestJob::OnResponseStarted"));
+
   // TODO(falken): Add Content-Length, Content-Type if they were not provided in
   // the ServiceWorkerResponse.
   response_time_ = base::Time::Now();
@@ -184,6 +190,11 @@ void ServiceWorkerURLRequestJob::OnResponseStarted(net::URLRequest* request) {
 
 void ServiceWorkerURLRequestJob::OnReadCompleted(net::URLRequest* request,
                                                  int bytes_read) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 ServiceWorkerURLRequestJob::OnReadCompleted"));
+
   SetStatus(request->status());
   if (!request->status().is_success()) {
     NotifyDone(request->status());