Cleanup: Pull some browser keep alive functions into its own file.

chrome/browser/app_controller_mac.h

Index: chrome/browser/app_controller_mac.h
diff --git a/chrome/browser/app_controller_mac.h b/chrome/browser/app_controller_mac.h
index b4bd63486d5c9e013223fc0c1b4d4941f604aa73..f08e5afc49a14c01bb05412b7c01faeb15ac61d0 100644
--- a/chrome/browser/app_controller_mac.h
+++ b/chrome/browser/app_controller_mac.h
@@ -30,6 +30,10 @@ class Profile;
 @class ProfileMenuController;
 class QuitWithAppsController;
 
+namespace browser_lifetime {
+class ScopedKeepAlive;
+}
+
 namespace ui {
 class WorkAreaWatcherObserver;
 }
@@ -92,6 +96,9 @@ class WorkAreaWatcherObserver;
   // Observers that listen to the work area changes.
   base::ObserverList<ui::WorkAreaWatcherObserver> workAreaChangeObservers_;
 
+  // Object to keep the browser alive when there are no windows open.
+  scoped_ptr<browser_lifetime::ScopedKeepAlive> keep_alive_;
+
   scoped_ptr<PrefChangeRegistrar> profilePrefRegistrar_;
   PrefChangeRegistrar localPrefRegistrar_;
 
@@ -185,4 +192,4 @@ bool IsOpeningNewWindow();
 
 }  // namespace app_controller_mac
 
-#endif
+#endif  // CHROME_BROWSER_APP_CONTROLLER_MAC_H_