Reason for revert:
Speculative revert for perf regression related to ramp-up on android. See https://bugs.chromium.org/p/chromium/issues/detail?id=682611
Original issue's description:
> Move congestion controller processing to the pacer thread.
>
> Also rename it from pacer_thread_ to congestion_controller_thread_.
>
> BUG=webrtc:6847
>
> Review-Url: https://codereview.webrtc.org/2637783003
> Cr-Commit-Position: refs/heads/master@{#16134}
> Committed: b3dc2b7b1e
TBR=danilchap@webrtc.org,stefan@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:6847
Review-Url: https://codereview.webrtc.org/2644603003
Cr-Commit-Position: refs/heads/master@{#16163}
Name: WebRTC URL: http://www.webrtc.org Version: 90 License: BSD License File: LICENSE Description: WebRTC provides real time voice and video processing functionality to enable the implementation of PeerConnection/MediaStream. Third party code used in this project is described in the file LICENSE_THIRD_PARTY.