[perf] Fix race condition.
[perf] Fix race condition.

Bug: skia:
Change-Id: I1f8a348a730aed2a85d0f3b1341cfe5adfc3e145
Reviewed-on: https://skia-review.googlesource.com/29601
Reviewed-by: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot