Allow media track switching.

media/base/audio_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_AUDIO_RENDERER_H_
 #define MEDIA_BASE_AUDIO_RENDERER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/time/time.h"
@@ skipping 14 matching lines @@
 
   // Stop all operations and fire all pending callbacks.
   virtual ~AudioRenderer();
 
   // Initialize an AudioRenderer 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.
+  //
+  // AudioRenderer 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 StartPlaying). This is used for
+  // media track switching.
   virtual void Initialize(DemuxerStream* stream,
                           CdmContext* cdm_context,
                           RendererClient* client,
                           const PipelineStatusCB& init_cb) = 0;
 
   // Returns the TimeSource associated with audio rendering.
   virtual TimeSource* GetTimeSource() = 0;
 
   // Discard any audio data, executing |callback| when completed.
   //
   // Clients should expect |buffering_state_cb| to be called with
   // BUFFERING_HAVE_NOTHING while flushing is in progress.
   virtual void Flush(const base::Closure& callback) = 0;
 
   // Starts playback by reading from |stream| and decoding and rendering audio.
   //
   // Only valid to call after a successful Initialize() or Flush().
   virtual void StartPlaying() = 0;
 
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioRenderer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_RENDERER_H_