RtpPacket doesn't keep difference between reserved and set extension. Bug: None Change-Id: I1c79f4ebd7ba20ae5da0194c3faa418050db7d8e Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/166340 Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#30316}