This adds tracking of traffic for streams that are part of bitrate
allocation but without packet feedback to send side congestion
controller.
This is part of a series of CLs that allows GoogCC to track sent bitrate
that is included in bitrate allocation but without transport feedback.
Bug: webrtc:9796
Change-Id: I13e994461c26638d76e8f2f115e6d375e4403116
Reviewed-on: https://webrtc-review.googlesource.com/c/104940
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Christoffer Rodbro <crodbro@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25126}