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;
+  bool success = base::PathService::Get(chrome::DIR_USER_DATA, &activity_file);
+  DCHECK(success);
+  activity_file = activity_file.AppendASCII("ActivityTracker");

[manzagop (departed), 2016/06/16 15:19:41]

Is there a "marketing concern" around the name ActivityTracker? We want it to be
clear this is Chrome's internal activity, not the user's. Also, tracking has a
precise meaning which is about mirroring the internal state. 

Perhaps a file named DebugState/DebugInfo or some such would communicate more
accurately to the user what this is?

The communication concern may not extend to the class's name though?

[bcwhite, 2016/06/16 17:04:43]

Good question.  I'm assuming that it being under "base::debug" is a sufficient
qualifier, plus the comments at the top of the file itself.

I can add a comment here, too.

[manzagop (departed), 2016/07/01 18:26:24]

Sgtm for the the code naming. 

For the file name, I think users finding an 'ActivityTracker' file in their user
data dir might wonder what it is, and it would be good to communicate this is
debug data.

[bcwhite, 2016/07/11 22:03:29]

Gotcha.  Done.

+  base::debug::SetupGlobalActivityTrackerFieldTrial(activity_file);
 }
 
 }  // namespace chrome