This cl prepares for a later CL introducing a new send side congestion
controller that will run on a task queue. It mostly consists of minor
fixes but adds some new interfaces that are unused in practice.
Bug: webrtc:8415
Change-Id: I1b58d0180a18eb15320d18733dac0dfe2e0f902a
Reviewed-on: https://webrtc-review.googlesource.com/53321
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22099}