Track thread activities in order to diagnose hangs.

chrome/browser/chrome_browser_field_trials_desktop.cc

 // Copyright 2013 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/chrome_browser_field_trials_desktop.h"
 
 #include <string>
 
 #include "base/command_line.h"
+#include "base/debug/activity_tracker.h"
 #include "base/metrics/field_trial.h"
+#include "base/path_service.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
+#include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/variations/variations_util.h"
 #include "components/variations/variations_associated_data.h"
 #include "content/public/common/content_switches.h"
 
 namespace chrome {
 
 namespace {
 
 void SetupLightSpeedTrials() {
@@ skipping 23 matching lines @@
       switches::kWebRtcStunProbeTrialParameter, cmd_param);
 #endif
 }
 
 }  // namespace
 
 void SetupDesktopFieldTrials(const base::CommandLine& parsed_command_line) {
   prerender::ConfigurePrerender(parsed_command_line);
   SetupLightSpeedTrials();
   SetupStunProbeTrial();
+
+  base::FilePath activity_file;
+  if (base::PathService::Get(chrome::DIR_USER_DATA, &activity_file))
+    activity_file = activity_file.AppendASCII("ActivityTracker");
+  base::debug::SetupGlobalActivityTrackerFieldTrial(activity_file);

[manzagop (departed), 2016/06/01 21:59:40]

Should this be inside the if?
If so, should you add uma metric for failures?

[bcwhite, 2016/06/02 16:18:16]

Get() should always return the same value for a given key at a given place in
the code.  I'll just turn this into a DCHECK.

 }
 
 }  // namespace chrome