ee3a86d8ab
This access is extremely infrequent, so we may as well consistently use the mutex. TEST=tsan Bug: https://github.com/dart-lang/sdk/issues/45521 Change-Id: I17b276f671e20c2eed8bf26735cc11c386fba9e6 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/194013 Reviewed-by: Alexander Aprelev <aam@google.com> Commit-Queue: Ryan Macnak <rmacnak@google.com>