Simplifying the use of signal transition and removing unused code. Bug: webrtc:8671 Change-Id: I0b845405727936b2fa7df7c92ad2e83bea3bc823 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/154348 Reviewed-by: Per Åhgren <peah@webrtc.org> Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29298}