Allow media track switching.

media/base/video_renderer.h

 // Copyright (c) 2012 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_VIDEO_RENDERER_H_
 #define MEDIA_BASE_VIDEO_RENDERER_H_
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "media/base/media_export.h"
@@ skipping 15 matching lines @@
 
   // Initializes a VideoRenderer with |stream|, executing |init_cb| upon
   // completion. If initialization fails, only |init_cb|
   // (not RendererClient::OnError) will be called.
   //
   // |cdm_context| can be used to handle encrypted streams. May be null if the
   // stream is not encrypted.
   //
   // |wall_clock_time_cb| is used to convert media timestamps into wallclock
   // timestamps.
+  //
+  // VideoRenderer may be reinitialized for playback of a different demuxer
+  // stream by calling Initialize again when the renderer is in a flushed
+  // state (i.e. after Flush call, but before StartPlayingFrom). This is used
+  // for media track switching.
   virtual void Initialize(DemuxerStream* stream,
                           CdmContext* cdm_context,
                           RendererClient* client,
                           const TimeSource::WallClockTimeCB& wall_clock_time_cb,
                           const PipelineStatusCB& init_cb) = 0;
 
   // Discards any video data and stops reading from |stream|, executing
   // |callback| when completed.
   //
   // Clients should expect |buffering_state_cb| to be called with
@@ skipping 12 matching lines @@
   virtual void OnTimeProgressing() = 0;
   virtual void OnTimeStopped() = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoRenderer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_RENDERER_H_