DefaultVideoQualityAnalyzerFramesComparator::Stop() may not block until
all frames comparisons are processed in case when new comparison was
added after worker thread checked for available comparisons and Stop()
was invoked before worker thread checked the state_.
Bug: webrtc:13277, webrtc:13240
Change-Id: Ic16fdc01e43c04529cd83e5d9ef66d7573973cfd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/235205
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35212}
46536e3da4