chromeos: Move files in //ash/common to //ash

ash/common/system/chromeos/screen_security/screen_share_observer.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_COMMON_SYSTEM_CHROMEOS_SCREEN_SECURITY_SCREEN_SHARE_OBSERVER_H_
-#define ASH_COMMON_SYSTEM_CHROMEOS_SCREEN_SECURITY_SCREEN_SHARE_OBSERVER_H_
-
-#include "base/callback.h"
-#include "base/strings/string16.h"
-
-namespace ash {
-
-class ScreenShareObserver {
- public:
-  // Called when screen share is started.
-  virtual void OnScreenShareStart(const base::Closure& stop_callback,
-                                  const base::string16& helper_name) = 0;
-
-  // Called when screen share is stopped.
-  virtual void OnScreenShareStop() = 0;
-
- protected:
-  virtual ~ScreenShareObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_SYSTEM_CHROMEOS_SCREEN_SECURITY_SCREEN_SHARE_OBSERVER_H_