Fix signedness of format string.

Change-Id: Id75ac23ee11f304a9f79f1ddc13846700f904d2f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/846599
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
1 file changed