Intorduce PowerButtonObserver API

athena/system/power_button_controller.h

-// Copyright 2014 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 ATHENA_SYSTEM_POWER_BUTTON_CONTROLLER_H_
-#define ATHENA_SYSTEM_POWER_BUTTON_CONTROLLER_H_
-
-#include "base/memory/scoped_ptr.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "chromeos/dbus/power_manager_client.h"
-
-namespace aura {
-class Window;
-}
-
-namespace views {
-class Widget;
-}
-
-namespace athena {
-
-// Shuts down in response to the power button being pressed.
-class PowerButtonController : public chromeos::PowerManagerClient::Observer {
- public:
-  explicit PowerButtonController(aura::Window* dialog_container);
-  virtual ~PowerButtonController();
-
- private:
-  enum State {
-    // Releasing the power button sends a suspend request.
-    STATE_SUSPEND_ON_RELEASE,
-
-    // A warning that the device is about to be shutdown is visible. Releasing
-    // the power button does not send a suspend or a shutdown request.
-    STATE_SHUTDOWN_WARNING_VISIBLE,
-
-    // A D-Bus shutdown request has been sent. Shutdown cannot be canceled.
-    STATE_SHUTDOWN_REQUESTED,
-
-    STATE_OTHER
-  };
-
-  // Shows the shutdown warning dialog.
-  void ShowShutdownWarningDialog();
-
-  // Requests shutdown.
-  void Shutdown();
-
-  // chromeos::PowerManagerClient::Observer:
-  virtual void BrightnessChanged(int level, bool user_initiated) override;
-  virtual void PowerButtonEventReceived(
-      bool down,
-      const base::TimeTicks& timestamp) override;
-
-  // |shutdown_warning_message_|'s parent container.
-  aura::Window* warning_message_container_;
-
-  // Shows a warning that the device is about to be shutdown.
-  scoped_ptr<views::Widget> shutdown_warning_message_;
-
-  // 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_;
-
-  State state_;
-
-  base::OneShotTimer<PowerButtonController> timer_;
-
-  DISALLOW_COPY_AND_ASSIGN(PowerButtonController);
-};
-
-}  // namespace athena
-
-#endif  // ATHENA_SYSTEM_POWER_BUTTON_CONTROLLER_H_