Media Remoting: Remove old interstitial implementation.

media/base/media_observer.h

 // Copyright 2016 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 MEDIA_BASE_MEDIA_OBSERVER_H_
 #define MEDIA_BASE_MEDIA_OBSERVER_H_
 
 #include "media/base/cdm_context.h"
 #include "media/base/pipeline_metadata.h"
 #include "url/gurl.h"
@@ skipping 38 matching lines @@
   // Called to indicate whether the site requests that remote playback be
   // disabled. The "disabled" naming corresponds with the
   // "disableRemotePlayback" media element attribute, as described in the
   // Remote Playback API spec: https://w3c.github.io/remote-playback
   virtual void OnRemotePlaybackDisabled(bool disabled) = 0;
 
   // Called when the media is playing/paused.
   virtual void OnPlaying() = 0;
   virtual void OnPaused() = 0;
 
-  // Called when a poster image URL is set, which happens when media is loaded
-  // or the poster attribute is changed.
-  virtual void OnSetPoster(const GURL& poster) = 0;
-
   // Set the MediaObserverClient.
   virtual void SetClient(MediaObserverClient* client) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_MEDIA_OBSERVER_H_