Fix race condition in GrGLCaps

Bug: 854778
Change-Id: I3421360a8549e231f508f28d3945d81f811e66de
Reviewed-on: https://skia-review.googlesource.com/138923
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed