[Cast] Repair receiver playout time calculations and frame skip logic.

media/cast/transport/cast_transport_config.h

Index: media/cast/transport/cast_transport_config.h
diff --git a/media/cast/transport/cast_transport_config.h b/media/cast/transport/cast_transport_config.h
index d72d1f8e32e26328835253adf56b19efb8c8c9b2..22ed4dd74d49c1a9360afeb9ccca1a9000f88dee 100644
--- a/media/cast/transport/cast_transport_config.h
+++ b/media/cast/transport/cast_transport_config.h
@@ -30,10 +30,12 @@ enum AudioCodec {
   kFakeSoftwareAudio,
   kOpus,
   kPcm16,
-  kExternalAudio,
-  kAudioCodecLast = kExternalAudio
+  kAudioCodecLast = kPcm16
 };
 
+bool CanDropFramesForCodec(AudioCodec audio_codec);
+bool CanDropFramesForCodec(VideoCodec video_codec);
+
 struct RtpConfig {
   RtpConfig();
   ~RtpConfig();