Remove KeyboardDevice class.

ui/events/devices/keyboard_device.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 UI_EVENTS_DEVICES_KEYBOARD_DEVICE_H_
-#define UI_EVENTS_DEVICES_KEYBOARD_DEVICE_H_
-
-#include <string>
-
-#include "ui/events/devices/events_devices_export.h"
-#include "ui/events/devices/input_device.h"
-
-namespace ui {
-
-// Represents a Keyboard device state.
-struct EVENTS_DEVICES_EXPORT KeyboardDevice : public InputDevice {
-  KeyboardDevice(int id, InputDeviceType type, const std::string& name);
-  explicit KeyboardDevice(const InputDevice& input_device);
-};
-
-}  // namespace ui
-
-#endif  // UI_EVENTS_DEVICES_KEYBOARD_DEVICE_H_