Refactors keyboard related code so mash can use a keyboard

ash/keyboard/keyboard_ui_observer.h

+// Copyright 2016 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_KEYBOARD_KEYBOARD_UI_OBSERVER_H_
+#define ASH_KEYBOARD_KEYBOARD_UI_OBSERVER_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace ash {
+
+class ASH_EXPORT KeyboardUIObserver {
+ public:
+  virtual void OnKeyboardEnabledStateChanged(bool new_value) = 0;
+
+ protected:
+  virtual ~KeyboardUIObserver() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_KEYBOARD_KEYBOARD_UI_OBSERVER_H_