Adds special support to the device manager for keyboards devices.

ui/events/input_device_event_observer.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_INPUT_DEVICE_EVENT_OBSERVER_H_
 #define UI_EVENTS_INPUT_DEVICE_EVENT_OBSERVER_H_
 
 namespace ui {
 
 // DeviceDataManager observer used to announce input hotplug events.
 class InputDeviceEventObserver {
  public:
   virtual ~InputDeviceEventObserver() {}
 
-  virtual void OnInputDeviceConfigurationChanged() = 0;
+  virtual void OnKeyboardDeviceConfigurationChanged() = 0;
+  virtual void OnTouchscreenDeviceConfigurationChanged() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_INPUT_DEVICE_EVENT_OBSERVER_H_