mash: Migrate remaining tray observers and notify functions.

ash/system/tray/media_security/media_capture_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_CHROMEOS_MEDIA_SECURITY_MEDIA_CAPTURE_OBSERVER_H_
-#define ASH_SYSTEM_CHROMEOS_MEDIA_SECURITY_MEDIA_CAPTURE_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace ash {
-
-class ASH_EXPORT MediaCaptureObserver {
- public:
-  // Called when media capture state has changed.
-  virtual void OnMediaCaptureChanged() = 0;
-
- protected:
-  virtual ~MediaCaptureObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_CHROMEOS_MEDIA_SECURITY_MEDIA_CAPTURE_OBSERVER_H_