Since many tests rely on rtc::Thread::Current(), add an explicit rtc::AutoThread in the main() function used by tests. Bug: webrtc:9714 Change-Id: Id82121967c9621fe1c2945846009c48139fa57da Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/39680 Reviewed-by: Kári Helgason <kthelgason@webrtc.org> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org> Commit-Queue: Niels Moller <nisse@webrtc.org> Cr-Commit-Position: refs/heads/master@{#28000}