Temporary patch for Mac TSAN bot (with threaded Ganesh mask generation)

Change-Id: Id84e1534b00583eb2d76699386f42277d2007602
Reviewed-on: https://skia-review.googlesource.com/49900
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed