Add BackgroundModeOptimizer that can restart the browser

chrome/browser/browser_shutdown.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_BROWSER_SHUTDOWN_H_
 #define CHROME_BROWSER_BROWSER_SHUTDOWN_H_
 
 #include "build/build_config.h"
 
 class PrefRegistrySimple;
 
 namespace browser_shutdown {
 
+// Shutdown flags
+enum Flags {
+  NO_FLAGS = 0,
+
+  // If |RESTART_LAST_SESSION| is set, the browser will attempt to restart in
+  // in the last session after the shutdown.
+  RESTART_LAST_SESSION = 1 << 0,
+
+  // Makes a panned restart happen in the background. The browser will just come
+  // up in the system tray but not open a new window after restarting. This flag
+  // has no effect if |RESTART_LAST_SESSION| is not set.
+  RESTART_IN_BACKGROUND = 1 << 1
+};
+
 enum ShutdownType {
   // an uninitialized value
   NOT_VALID = 0,
   // the last browser window was closed
   WINDOW_CLOSE,
   // user clicked on the Exit menu item
   BROWSER_EXIT,
   // windows is logging off or shutting down
   END_SESSION
 };
@@ skipping 10 matching lines @@
 #if !defined(OS_ANDROID)
 // Performs the shutdown tasks that need to be done before
 // BrowserProcess and the various threads go away.
 //
 // Returns true if the session should be restarted.
 bool ShutdownPreThreadsStop();
 
 // Performs the remaining shutdown tasks after all threads but the
 // main thread have been stopped.  This includes deleting g_browser_process.
 //
-// The provided parameter indicates whether a preference to restart
-// the session was present.
-void ShutdownPostThreadsStop(bool restart_last_session);
+// See |browser_shutdown::Flags| for the possible flag values and their effects.
+void ShutdownPostThreadsStop(int shutdown_flags);
 #endif
 
 // Called at startup to create a histogram from our previous shutdown time.
 void ReadLastShutdownInfo();
 
 // There are various situations where the browser process should continue to
 // run after the last browser window has closed - the Mac always continues
 // running until the user explicitly quits, and on Windows/Linux the application
 // should not shutdown when the last browser window closes if there are any
 // BackgroundContents running.
@@ skipping 14 matching lines @@
 bool IsTryingToQuit();
 
 // 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();
 
 }  // namespace browser_shutdown
 
 #endif  // CHROME_BROWSER_BROWSER_SHUTDOWN_H_