Add fade to white animation when power button is pressed on Athena

athena/system/power_button_controller.h

Index: athena/system/power_button_controller.h
diff --git a/athena/system/power_button_controller.h b/athena/system/power_button_controller.h
index 69fa9a8ac71538b4971a2539cebd03a058bf25ec..0d4bd0e50b609069573f45c7df9a08bab221681d 100644
--- a/athena/system/power_button_controller.h
+++ b/athena/system/power_button_controller.h
@@ -5,31 +5,52 @@
 #ifndef ATHENA_SYSTEM_POWER_BUTTON_CONTROLLER_H_
 #define ATHENA_SYSTEM_POWER_BUTTON_CONTROLLER_H_
 
+#include "base/time/time.h"
 #include "chromeos/dbus/power_manager_client.h"
+#include "ui/compositor/layer_animation_observer.h"
+#include "ui/gfx/animation/tween.h"
 
 namespace athena {
 
 // Shuts down in response to the power button being pressed.
-class PowerButtonController : public chromeos::PowerManagerClient::Observer {
+class PowerButtonController : public chromeos::PowerManagerClient::Observer,
+                              public ui::ImplicitAnimationObserver {
  public:
   PowerButtonController();
   virtual ~PowerButtonController();
 
+ private:
+  enum State {
+    // The screen is animating prior to shutdown. Shutdown can be canceled.
+    STATE_PRE_SHUTDOWN_ANIMATION,
+
+    // A D-Bus shutdown request has been sent. Shutdown cannot be canceled.
+    STATE_SHUTDOWN_REQUESTED,
+
+    STATE_OTHER
+  };
+
+  // Animates the screen's grayscale and brightness to |target|.
+  void StartGrayscaleAndBrightnessAnimation(float target,
+                                            int duration_ms,
+                                            gfx::Tween::Type tween_type);
+
   // chromeos::PowerManagerClient::Observer:
   virtual void BrightnessChanged(int level, bool user_initiated) OVERRIDE;
   virtual void PowerButtonEventReceived(
       bool down,
       const base::TimeTicks& timestamp) OVERRIDE;
 
- private:
+  // ui::ImplicitAnimationObserver:
+  virtual void OnImplicitAnimationsCompleted() OVERRIDE;
+
   // Whether the screen brightness was reduced to 0%.
   bool brightness_is_zero_;
 
   // The last time at which the screen brightness was 0%.
   base::TimeTicks zero_brightness_end_time_;
 
-  // Whether shutdown was requested.
-  bool shutdown_requested_;
+  State state_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerButtonController);
 };