The purpose is to be able to create a RtpPacketSendInfo from Pacing and RtpPacketSendInfo only. This allow further refactoring where we directly in PacketRouter can notify BWE and early loss detection that a packet will be sent. RtpPacketSendInfo::From is mostly added to be able to test conversion. Bug: webrtc:15368 Change-Id: I5ebe2dc91d2eedf2c86e62c3f9738437082a49e4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/343766 Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Commit-Queue: Per Kjellander <perkj@webrtc.org> Cr-Commit-Position: refs/heads/main@{#41961}