limit mask drawing to clip bounds

Change-Id: Iab74531614654f241e12d1cd1af14725888580c8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207143
Reviewed-by: Mike Reed <reed@google.com>
Auto-Submit: Lee Salzman <lsalzman@mozilla.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed