mash: Migrate [Keyboard]Brightness code to ash/common.

ash/system/chromeos/brightness/brightness_controller_chromeos.h

-// Copyright 2013 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 ASH_SYSTEM_CHROMEOS_BRIGHTNESS_BRIGHTNESS_CONTROLLER_CHROMEOS_H_
-#define ASH_SYSTEM_CHROMEOS_BRIGHTNESS_BRIGHTNESS_CONTROLLER_CHROMEOS_H_
-
-#include "ash/ash_export.h"
-#include "ash/system/brightness_control_delegate.h"
-#include "base/compiler_specific.h"
-#include "base/macros.h"
-
-namespace ash {
-namespace system {
-
-// A class which controls brightness when F6, F7 or a multimedia key for
-// brightness is pressed.
-class ASH_EXPORT BrightnessControllerChromeos
-    : public ash::BrightnessControlDelegate {
- public:
-  BrightnessControllerChromeos() {}
-  ~BrightnessControllerChromeos() override {}
-
-  // Overridden from ash::BrightnessControlDelegate:
-  void HandleBrightnessDown(const ui::Accelerator& accelerator) override;
-  void HandleBrightnessUp(const ui::Accelerator& accelerator) override;
-  void SetBrightnessPercent(double percent, bool gradual) override;
-  void GetBrightnessPercent(
-      const base::Callback<void(double)>& callback) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BrightnessControllerChromeos);
-};
-
-}  // namespace system
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_CHROMEOS_BRIGHTNESS_BRIGHTNESS_CONTROLLER_CHROMEOS_H_