This reland https://codereview.webrtc.org/1655793003/ with the change that cricket::VideoCapturer::SignalVideoFrame is added back and used for frame forwarding. It is used in Chrome remoting.

BUG=webrtc:5426
R=pthatcher@webrtc.org
TBR=pthatcher@webrtc.org for moved channelmanager....

Review URL: https://codereview.webrtc.org/1689923002 .

Cr-Original-Commit-Position: refs/heads/master@{#11597}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a50924115e47f052a61dc146e350b0677cd2ebd9
22 files changed