This is a part of series of CLs adding PCC (Performance-oriented Congestion Control). Bug: webrtc:9434 Change-Id: Idd36d8abea008623ac64b939d0de7ee6001f7f23 Reviewed-on: https://webrtc-review.googlesource.com/86951 Commit-Queue: Anastasia Koloskova <koloskova@webrtc.org> Reviewed-by: Sebastian Jansson <srte@webrtc.org> Reviewed-by: Björn Terelius <terelius@webrtc.org> Cr-Commit-Position: refs/heads/master@{#24364}