[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"
+#include "content/public/browser/presentation_service_delegate.h"
 
 namespace media_router {
 
 class MediaRouter;
 
-// Base class for observing state changes on a PresentationConnection.
+// Observes state changes on a PresentationConnection and returns the new state

[mark a. foltz, 2015/11/12 04:19:38]

Is the caller expected to find out the current state of the
PresentationConnection via some other means - then add the observer?

[imcheng, 2015/11/16 23:52:01]

For our current use case, it is not needed. We start listening when the route is
created, and it is assumed to be in the initial state (connected).

+// to the supplied PresentationConnectionStateChangedCallback.

[mark a. foltz, 2015/11/12 04:19:38]

Clarify that this callback is run multiple times - once per state change.

[imcheng, 2015/11/16 23:52:01]

Done in media_router.h.

 class PresentationConnectionStateObserver {
  public:
+  // |state_changed_cb|: The callback to invoke with state changes.
   // |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);
+  PresentationConnectionStateObserver(
+      const content::PresentationConnectionStateChangedCallback&
+          state_changed_cb,
+      const content::PresentationSessionInfo& connection,
+      const MediaRoute::Id& route_id,
+      MediaRouter* router);
   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) {}
+  void OnStateChanged(content::PresentationConnectionState state);
 
  private:
+  const content::PresentationConnectionStateChangedCallback state_changed_cb_;
+  const content::PresentationSessionInfo connection_;
+  const MediaRoute::Id route_id_;
   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_