The RTP payload type was changed to indicate both media type and codec. However,
Fugu receivers expect the RTP payload type to be 127 for audio, and 96 for video specifically. This constraint should be removed from receiver codes. For now, sender will override this value as required.

Patch for review: https://codereview.chromium.org/2179943004

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cae9d55680876b8c22acdd6c3e3cd38a57d7fc14

commit cae9d55680876b8c22acdd6c3e3cd38a57d7fc14
Author: xjz <xjz@chromium.org>
Date: Wed Jul 27 04:21:13 2016

Set the RTP payload type to fixed values for audio/video streams.
Fugu receivers expect specific RTP payload type for audio/video
streams. This constraint should be removed from receiver codes. For
now, sender will override the payload type with the required value in
each RTP packet.

BUG= 631828 

Review-Url: https://codereview.chromium.org/2179943004
Cr-Commit-Position: refs/heads/master@{#408038}

[modify] https://crrev.com/cae9d55680876b8c22acdd6c3e3cd38a57d7fc14/media/cast/net/rtp/rtp_sender.cc
[modify] https://crrev.com/cae9d55680876b8c22acdd6c3e3cd38a57d7fc14/media/cast/receiver/frame_receiver.cc