Revert "chromeos: Move files in //ash/common to //ash, part 1"

ash/system/virtual_keyboard/virtual_keyboard_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 ASH_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_OBSERVER_H_
-#define ASH_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace ash {
-
-class ASH_EXPORT VirtualKeyboardObserver {
- public:
-  virtual ~VirtualKeyboardObserver() {}
-
-  // Notifies when the keyboard is suppressed.
-  virtual void OnKeyboardSuppressionChanged(bool suppressed) = 0;
-};
-
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_OBSERVER_H_