contributing sources are usually decided per packet, and thus having persistent member for csrcs makes them less natural to use. Bug: None Change-Id: I804d58ace574368f8cdd4356a15471110e530744 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/291334 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Åsa Persson <asapersson@webrtc.org> Cr-Commit-Position: refs/heads/main@{#40547}