Adding shutdown tracing capabilities

chrome/browser/lifetime/application_lifetime.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_LIFETIME_APPLICATION_LIFETIME_H_
 #define CHROME_BROWSER_LIFETIME_APPLICATION_LIFETIME_H_
 
 class Browser;
 
 namespace chrome {
 
 // Starts a user initiated exit process. Called from Browser::Exit.
 // On platforms other than ChromeOS, this is equivalent to
 // CloseAllBrowsers() On ChromeOS, this tells session manager
 // that chrome is signing out, which lets session manager send
 // SIGTERM to start actual exit process.
 void AttemptUserExit();
 
+// Starts to collect shutdown traces. On ChromeOS this will start immediately
+// on AttemptUserExit() and all other systems will start once all tabs are
+// closed.
+void StartShutdownTracing();
+
 // Starts a user initiated restart process. On platforms other than
 // chromeos, this sets a restart bit in the preference so that
 // chrome will be restarted at the end of shutdown process. On
 // ChromeOS, this simply exits the chrome, which lets sesssion
 // manager re-launch the browser with restore last session flag.
 void AttemptRestart();
 
 #if defined(OS_WIN)
 // Windows 8 specific: Like AttemptRestart but if chrome is running
 // in desktop mode it starts in metro mode and vice-versa. The switching like
@@ skipping 56 matching lines @@
 // processing required.
 void HandleAppExitingForPlatform();
 
 // Returns true if we can start the shutdown sequence for the browser, i.e. the
 // last browser window is being closed.
 bool ShouldStartShutdown(Browser* browser);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_LIFETIME_APPLICATION_LIFETIME_H_