Class was introduced in 2017, see
https://webrtc-review.googlesource.com/1420, but never taken into use.
Bug: chromium:764258
Change-Id: I5f15f25a3c1a992f8c725b78891956e7275b0e4d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/194320
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32665}