Existing test would only check the channel was not open instead of checking for a proper transition to closing then closed. Bug: webrtc:12614 Change-Id: Iab74d6252ca1411c0fe8c1ee4ca09bc6d81af90c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/216388 Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Florent Castelli <orphis@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33874}