Destroying a mutex while it is held is never valid, and can be extremely
hard to debug.
Change-Id: I42ff79de7892006337f204621ff59bf84112dcd7
Bug: skia:12943
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/507998
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>