[Cast] Track audio queued in encoder; account for it in ShouldDropNextFrame().

media/cast/sender/audio_sender.h

Index: media/cast/sender/audio_sender.h
diff --git a/media/cast/sender/audio_sender.h b/media/cast/sender/audio_sender.h
index bef042a24246154d6b3df9a70c3f0db9afa620e7..b307bf84e4c7cbd0fcebca214656c976373d7fe7 100644
--- a/media/cast/sender/audio_sender.h
+++ b/media/cast/sender/audio_sender.h
@@ -55,19 +55,21 @@ class AudioSender : public FrameSender,
   void OnReceivedCastFeedback(const RtcpCastMessage& cast_feedback);
 
  private:
-  // Returns true if there are too many frames in flight, or if the media
-  // duration of the frames in flight would be too high by sending the next
-  // frame.  The latter metric is determined from the given |capture_time|
-  // for the next frame to be encoded and sent.
-  bool ShouldDropNextFrame(base::TimeTicks capture_time) const;
+  // Recompute |samples_in_encoder_| as well as the duration and number of
+  // frames enqueued in the encoder.
+  void UpdateEncoderBacklogStats(int samples_added);
 
   // Called by the |audio_encoder_| with the next EncodedFrame to send.
-  void SendEncodedAudioFrame(scoped_ptr<EncodedFrame> audio_frame);
+  void SendEncodedAudioFrame(scoped_ptr<EncodedFrame> audio_frame,
+                             int samples_skipped);
 
   // Encodes AudioBuses into EncodedFrames.
   scoped_ptr<AudioEncoder> audio_encoder_;
   const int configured_encoder_bitrate_;
 
+  // The number of audio samples enqueued in |audio_encoder_|.
+  int samples_in_encoder_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<AudioSender> weak_factory_;