use SkRect::outset, as it clamps on overflow

Bug: oss-fuzz:7929
Change-Id: Ic9a2582eb7ab638fda71b10bf987a6c584770e43
Reviewed-on: https://skia-review.googlesource.com/122959
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed