Adding instrumentation to locate the source of jankiness.

chrome/browser/net/connection_tester.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/net/connection_tester.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/thread_restrictions.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/cookie_store_factory.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_util.h"
 #include "net/base/request_priority.h"
@@ skipping 313 matching lines @@
   scoped_ptr<ExperimentURLRequestContext> request_context_;
   scoped_ptr<net::URLRequest> request_;
   net::NetLog* net_log_;
 
   base::WeakPtrFactory<TestRunner> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TestRunner);
 };
 
 void ConnectionTester::TestRunner::OnResponseStarted(net::URLRequest* request) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422516 ConnectionTester::TestRunner::OnResponseStarted"));
+
   if (!request->status().is_success()) {
     OnResponseCompleted(request);
     return;
   }
 
   // Start reading the body.
   ReadBody(request);
 }
 
 void ConnectionTester::TestRunner::OnReadCompleted(net::URLRequest* request,
                                                    int bytes_read) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422516 ConnectionTester::TestRunner::OnReadCompleted"));

[mmenke, 2014/11/17 15:38:16]

This file is not worth instrumenting.  It's only used from about:net-internals,
when manually triggered.  So it's not used often enough to be a common cause of
jank...And even if it were, we don't care.  That's basically internal-only API
intended for Chrome development / debugging (Not general web development).

[vadimt, 2014/11/18 01:14:27]

Done.

+
   if (bytes_read <= 0) {
     OnResponseCompleted(request);
     return;
   }
 
   // Keep reading until the stream is closed. Throw the data read away.
   ReadBody(request);
 }
 
 void ConnectionTester::TestRunner::ReadBody(net::URLRequest* request) {
@@ skipping 166 matching lines @@
 
   // Notify the delegate of completion.
   delegate_->OnCompletedConnectionTestExperiment(current, result);
 
   if (remaining_experiments_.empty()) {
     delegate_->OnCompletedConnectionTestSuite();
   } else {
     StartNextExperiment();
   }
 }