Use a map of packet sizes in RtpPacketHistory instead of looping through the whole history for every call. Bug: webrtc:9731 Change-Id: I44a4f6221e261a6cb3d5039edfa7556a102ee6f1 Reviewed-on: https://webrtc-review.googlesource.com/98882 Reviewed-by: Erik Språng <sprang@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Commit-Queue: Per Kjellander <perkj@webrtc.org> Cr-Commit-Position: refs/heads/master@{#24662}