This code has been unused for years, and at least the RTCP RSPI sending logic appears broken. This cl is part 3, following https://codereview.webrtc.org/2746413003 (delete sending) https://codereview.webrtc.org/2753783002 (delete vp8 feedback mode) BUG=webrtc:7338 Review-Url: https://codereview.webrtc.org/2742383004 Cr-Commit-Position: refs/heads/master@{#17342}