Prevent JS from bypassing RTP data channel bandwidth limitation.

Normally the RTP data channel is capped at 30kbps, but by mangling the
SDP string, one could get around this limitation. With this fix,
SdpDeserialize will return an error if it detects this condition.

BUG=280726
R=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1196403004.

Cr-Commit-Position: refs/heads/master@{#9499}
2 files changed