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 2f08927ccab2034a515ff1cb8a4bf41642431dee..33c0d7535fcd54ff5204ab98c7a710ac772db23d 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -68,6 +68,7 @@ class Launcher;
 class NestedDispatcherController;
 class PowerButtonController;
 class ScreenAsh;
+class SessionStateController;
 class ShellDelegate;
 class ShellObserver;
 class SystemTrayDelegate;
@@ -273,6 +274,9 @@ class ASH_EXPORT Shell : internal::SystemModalContainerEventFilterDelegate{
   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();
   }
@@ -444,6 +448,7 @@ class ASH_EXPORT Shell : internal::SystemModalContainerEventFilterDelegate{
   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_;