ash : Decouple power button controller and session state controller.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index ef869bf447ce7138e5f0c7e43a6d7d99518f4a23..2fc1b77eac1d7307ea8e07e4817a6e684a44f241 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -67,6 +67,7 @@ class HighContrastController;
 class Launcher;
 class NestedDispatcherController;
 class PowerButtonController;
+class SessionStateController;
 class ScreenAsh;
 class ShellDelegate;
 class ShellObserver;
@@ -266,6 +267,9 @@ class ASH_EXPORT Shell : CursorDelegate,
   PowerButtonController* power_button_controller() {
     return power_button_controller_.get();
   }
+  SessionStateController* session_state_controller() {
+    return session_state_controller_.get();
+  }
   UserActivityDetector* user_activity_detector() {
     return user_activity_detector_.get();
   }
@@ -445,6 +449,7 @@ class ASH_EXPORT Shell : CursorDelegate,
   scoped_ptr<internal::VisibilityController> visibility_controller_;
   scoped_ptr<DesktopBackgroundController> desktop_background_controller_;
   scoped_ptr<PowerButtonController> power_button_controller_;
+  scoped_ptr<SessionStateController> session_state_controller_;
   scoped_ptr<UserActivityDetector> user_activity_detector_;
   scoped_ptr<VideoDetector> video_detector_;
   scoped_ptr<WindowCycleController> window_cycle_controller_;