This CL adds a function to the SendSideCongestionController interface
for reporting per packet feedback availability.
This is part of a series of CLs tracking the transport feedback status
of the streams known to BitrateAllocator and reporting the status to
the congestion controller.
Bug: webrtc:8415
Change-Id: Ifcb6837bb80c5fcfc1f12f4f93ec38cc2903118f
Reviewed-on: https://webrtc-review.googlesource.com/63205
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22565}