(reverted in https://webrtc-review.googlesource.com/c/src/+/123182/1) Original cl description: Always offer transport sequence number header extension for audio If the extension is negotiated, it will only be used if the field trial WebRTC-Audio-SendSideBwe is enabled. This allows simpler experimentation if it should be used or not. Patchset 3 contain the only change: Add the field trial WebRTC-Audio-SendSideBwe to call/rampup_tests.cc TBR: srte@webrtc.org,ossu@webrtc.org Bug: webrtc:10309 webrtc:10286 Change-Id: I2c1224e8a9fab52c1030369c1364686322e88a0f Reviewed-on: https://webrtc-review.googlesource.com/c/123183 Commit-Queue: Per Kjellander <perkj@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Cr-Commit-Position: refs/heads/master@{#26706}