Revert of Update AudioRenderer API to fire changes in BufferingState.

media/base/audio_renderer.h

Index: media/base/audio_renderer.h
diff --git a/media/base/audio_renderer.h b/media/base/audio_renderer.h
index e62d05f290d8e0ff66ed9b7a0b1b582e3ca88a36..2d7d3e18a2bce90a74353d283df90de8bcb7aca0 100644
--- a/media/base/audio_renderer.h
+++ b/media/base/audio_renderer.h
@@ -8,7 +8,6 @@
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
-#include "media/base/buffering_state.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
 
@@ -22,9 +21,6 @@
   // Second parameter is the maximum time value that the clock cannot exceed.
   typedef base::Callback<void(base::TimeDelta, base::TimeDelta)> TimeCB;
 
-  // Used to indicate changes in the buffering state of this audio renderer.
-  typedef base::Callback<void(BufferingState)> BufferingStateCB;
-
   AudioRenderer();
   virtual ~AudioRenderer();
 
@@ -33,10 +29,12 @@
   //
   // |statistics_cb| is executed periodically with audio rendering stats.
   //
+  // |underflow_cb| is executed when the renderer runs out of data to pass to
+  // the audio card during playback. ResumeAfterUnderflow() must be called
+  // to resume playback. Pause(), Preroll(), or Stop() cancels the underflow
+  // condition.
+  //
   // |time_cb| is executed whenever time has advanced by way of audio rendering.
-  //
-  // |buffering_state_cb| is executed when audio rendering has either ran out of
-  // data or has enough data to continue playback.
   //
   // |ended_cb| is executed when audio rendering has reached the end of stream.
   //
@@ -44,8 +42,8 @@
   virtual void Initialize(DemuxerStream* stream,
                           const PipelineStatusCB& init_cb,
                           const StatisticsCB& statistics_cb,
+                          const base::Closure& underflow_cb,
                           const TimeCB& time_cb,
-                          const BufferingStateCB& buffering_state_cb,
                           const base::Closure& ended_cb,
                           const PipelineStatusCB& error_cb) = 0;
 
@@ -58,16 +56,14 @@
   virtual void StopRendering() = 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.
-  // |timestamp| is the media timestamp playback should start rendering from.
+  // Start prerolling audio data for samples starting at |time|, executing
+  // |callback| when completed.
   //
   // Only valid to call after a successful Initialize() or Flush().
-  virtual void StartPlayingFrom(base::TimeDelta timestamp) = 0;
+  virtual void Preroll(base::TimeDelta time,
+                       const PipelineStatusCB& callback) = 0;
 
   // Stop all operations in preparation for being deleted, executing |callback|
   // when complete.
@@ -79,6 +75,9 @@
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;
 
+  // Resumes playback after underflow occurs.
+  virtual void ResumeAfterUnderflow() = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioRenderer);
 };