With L4S in WebRTC, only RTP packets are supposed to be send with ECT(1) Bug: webrtc:42225697 Change-Id: If10bf74a867d3ea04fd1fb931cdc2a6380176270 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/367220 Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Per Kjellander <perkj@webrtc.org> Cr-Commit-Position: refs/heads/main@{#43343}