When bundling is in effect, multiple senders may be sharing the same
transport. It means every |sent_packet| will be multiply notified from
different channels, WebRtcVoiceMediaChannel or WebRtcVideoChannel.
Record |last_sent_packet_| to deduplicate redundant notifications to
downstream objects.
This CL reduces 50% PostTask/Wakeup of Dynamic Mode Pacer.
[1] https://datatracker.ietf.org/doc/html/rfc8829#section-4.1.1
[2] https://datatracker.ietf.org/doc/html/rfc8843
Bug: webrtc:13417
Change-Id: Ib121d5af07abe208bd7d36715a234f48cdabb032
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/238720
Reviewed-by: Markus Handell <handellm@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Markus Handell <handellm@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35417}
61a8d9caaa