Extract locking behaviour from ProcessSingleton.

chrome/browser/chrome_browser_main.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 #define CHROME_BROWSER_CHROME_BROWSER_MAIN_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/tracked_objects.h"
 #include "chrome/browser/chrome_browser_field_trials.h"
 #include "chrome/browser/first_run/first_run.h"
 #include "chrome/browser/process_singleton.h"
+#include "chrome/browser/process_singleton_modal_dialog_lock.h"
+#include "chrome/browser/process_singleton_startup_lock.h"
 #include "chrome/browser/task_profiler/auto_tracking.h"
 #include "chrome/browser/ui/startup/startup_browser_creator.h"
 #include "content/public/browser/browser_main_parts.h"
 
 class ActiveTabTracker;
 class BrowserProcessImpl;
 class ChromeBrowserMainExtraParts;
 class FieldTrialSynchronizer;
 class MetricsService;
 class PrefService;
@@ skipping 135 matching lines @@
 
   scoped_ptr<BrowserProcessImpl> browser_process_;
   scoped_refptr<chrome_browser_metrics::TrackingSynchronizer>
       tracking_synchronizer_;
 #if !defined(OS_ANDROID)
   // Browser creation happens on the Java side in Android.
   scoped_ptr<StartupBrowserCreator> browser_creator_;
 
   // Android doesn't support multiple browser processes, so it doesn't implement
   // ProcessSingleton.
+  ProcessSingletonStartupLock startup_lock_;
+  ProcessSingletonModalDialogLock modal_dialog_lock_;
   scoped_ptr<ProcessSingleton> process_singleton_;

[Nico, 2013/04/17 21:04:24]

I started reviewing this a few times, and always got confused somewhere down the
road. I think my main problem is that I don't understand what all these locks
mean.

Can you add comments here that explain:
a) What each lock is for and when it's held
b) The locking hierarchy, i.e. the order these locks have to be obtained in
?

 #endif
   scoped_ptr<first_run::MasterPrefs> master_prefs_;
   bool record_search_engine_;
   TranslateManager* translate_manager_;
   Profile* profile_;
   bool run_message_loop_;
   ProcessSingleton::NotifyResult notify_result_;
   scoped_ptr<ThreeDAPIObserver> three_d_observer_;
 
   // Initialized in SetupMetricsAndFieldTrials.
@@ skipping 32 matching lines @@
 // Records the time from our process' startup to the present time in
 // the Startup.BrowserMessageLoopStartTime UMA histogram.
 void RecordBrowserStartupTime();
 
 // Records a time value to an UMA histogram in the context of the
 // PreReadExperiment field-trial. This also reports to the appropriate
 // sub-histogram (_PreRead(Enabled|Disabled)).
 void RecordPreReadExperimentTime(const char* name, base::TimeDelta time);
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_MAIN_H_