[Media Router] Connection state change listening redesign part 2.

chrome/browser/media/router/presentation_connection_state_observer.h

-// Copyright 2015 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 CHROME_BROWSER_MEDIA_ROUTER_PRESENTATION_CONNECTION_STATE_OBSERVER_H_
-#define CHROME_BROWSER_MEDIA_ROUTER_PRESENTATION_CONNECTION_STATE_OBSERVER_H_
-
-#include "base/macros.h"
-#include "chrome/browser/media/router/media_route.h"
-
-namespace media_router {
-
-class MediaRouter;
-
-// Base class for observing state changes on a PresentationConnection.
-class PresentationConnectionStateObserver {
- public:
-  // |router|: The MediaRouter instance to register this instance with.
-  // |route_id|: ID of MediaRoute connected to the PresentationConnection to
-  // be observed.
-  PresentationConnectionStateObserver(MediaRouter* router,
-                                      const MediaRoute::Id& route_id);
-  virtual ~PresentationConnectionStateObserver();
-
-  MediaRoute::Id route_id() const { return route_id_; }
-
-  // Invoked when the state of PresentationConnection represented by |route_id_|
-  // has changed to |state|.
-  virtual void OnStateChanged(content::PresentationConnectionState state) {}
-
- private:
-  MediaRouter* const router_;
-  const MediaRoute::Id route_id_;
-
-  DISALLOW_COPY_AND_ASSIGN(PresentationConnectionStateObserver);
-};
-
-}  // namespace media_router
-
-#endif  // CHROME_BROWSER_MEDIA_ROUTER_PRESENTATION_CONNECTION_STATE_OBSERVER_H_