PacketArrivalMap explicitly doesn't promise packet at the beginning of it is received. Ensuring that property is wasteful Bug: chromium:1382563 Change-Id: Ifc898b7ec2bc7a302af8dcfd233e0c598f62db95 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290501 Reviewed-by: Per Kjellander <perkj@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39083}