Add BackgroundModeOptimizer that can restart the browser

chrome/browser/lifetime/application_lifetime.h

Index: chrome/browser/lifetime/application_lifetime.h
diff --git a/chrome/browser/lifetime/application_lifetime.h b/chrome/browser/lifetime/application_lifetime.h
index 2d426ae8a94698cd3acf939ab2f1a6f93be81b18..bd3ed32ffc94543d34eca983d10ce17fd47e9043 100644
--- a/chrome/browser/lifetime/application_lifetime.h
+++ b/chrome/browser/lifetime/application_lifetime.h
@@ -85,6 +85,12 @@ void OnAppExiting();
 // Called once the application is exiting to do any platform specific
 // processing required.
 void HandleAppExitingForPlatform();
+
+// Calling |AttemptRestart| unconditionally sets some preference to be used

[sky, 2016/07/06 16:55:33]

nit: generally | is used for arguments and members, where as () is used for
functions, e.g. AttemptRestart().

[dgn, 2016/07/22 15:18:09]

Ack.

+// during the shutdown or start sequences. They normally get reset when they are
+// individually read and used. In case a restart is cancelled, this function
+// should be called to perform that reset.
+void ResetRestartPrefs();

[sky, 2016/07/06 16:55:33]

Can this move to browser_shutdown::SetTryingToQuit if quitting is false? Having
this public is confusing and not something we normally want folks calling,
right?

[dgn, 2016/07/22 15:18:09]

Good point, done.

 #endif  // !defined(OS_ANDROID)
 
 }  // namespace chrome