This will enable wiring up these signals to the platform specific capturers Bug: chromium:1116430 Change-Id: I6cdab61eab202a24fa56167da57c389a5b1880c2 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/182683 Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32017}