It turned out that the negotiated rtp header extensions are not fully known in WebRtcVideoChannel::AddSendStream.
The cl also remove the unnecessary factory for creating VideoStreamEncoder.
Bug: webrtc:12000
Change-Id: If994c8deb69f3ce4212896d3ad757dac94c6e09f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/198840
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32916}