Revert of Update AudioRenderer API to fire changes in BufferingState.

media/base/pipeline.h

Index: media/base/pipeline.h
diff --git a/media/base/pipeline.h b/media/base/pipeline.h
index 6c073da6255c6a768c141dece870536b3b94764f..b40cd3c98c798844906682ae2c43291bc401277f 100644
--- a/media/base/pipeline.h
+++ b/media/base/pipeline.h
@@ -309,6 +309,8 @@
   void DoStop(const PipelineStatusCB& done_cb);
   void OnStopCompleted(PipelineStatus status);
 
+  void OnAudioUnderflow();
+
   // Collection of callback methods and helpers for tracking changes in
   // buffering state and transition from paused/underflow states and playing
   // states.
@@ -317,11 +319,11 @@
   //   - A waiting to non-waiting transition indicates preroll has completed
   //     and StartPlayback() should be called
   //   - A non-waiting to waiting transition indicates underflow has occurred
-  //     and PausePlayback() should be called
+  //     and StartWaitingForEnoughData() should be called
   void BufferingStateChanged(BufferingState* buffering_state,
                              BufferingState new_buffering_state);
   bool WaitingForEnoughData() const;
-  void PausePlayback();
+  void StartWaitingForEnoughData();
   void StartPlayback();
 
   void PauseClockAndStopRendering_Locked();