Expose the "debug" mutex so insertPerfWarning can use it. This was detected using TSAN and MultithreadingTest. Bug: b/168744561 Change-Id: Idde95a7b217f21f007893192a4a1f0a69b4ed3a9 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2415184 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
