[chromecast] Deletes dead code to track MediaPipelineBackend.

chromecast/media/cma/pipeline/media_pipeline_client.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 CHROMECAST_MEDIA_CMA_PIPELINE_MEDIA_PIPELINE_CLIENT_H_
 #define CHROMECAST_MEDIA_CMA_PIPELINE_MEDIA_PIPELINE_CLIENT_H_
 
 #include "base/callback.h"
 #include "base/time/time.h"
 #include "media/base/buffering_state.h"
@@ skipping 12 matching lines @@
 
   // Callback used to report a playback error as a ::media::PipelineStatus.
   ::media::PipelineStatusCB error_cb;
 
   // Callback used to report the latest playback time,
   // as well as the maximum time available for rendering.
   TimeUpdateCB time_update_cb;
 
   // Callback used to report the buffering status.
   ::media::BufferingStateCB buffering_state_cb;
-
-  // Callback used to report the creation and destruction of
-  // MediaPipelineBackend
-  base::Closure pipeline_backend_created_cb;
-  base::Closure pipeline_backend_destroyed_cb;
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CMA_PIPELINE_MEDIA_PIPELINE_CLIENT_H_