This code used to have a reader-writer lock, and call std::queue::pop() with only a reader lock, which appears unsafe. Code changed to use a plain webrtc::Mutex. Bug: webrtc:12102 Change-Id: Icbea17a824c91975dfebd4d05bbd0c21e1abeadc Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/190700 Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org> Commit-Queue: Niels Moller <nisse@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32511}