Initialize mask to 0 during AntiRect optimization

Previously, the mask is uninitialized (which is probably caught by
MSAN) for the region to the left and right of fAntiRect when
fAntiRect is non-empty. That causes skbug.com/7192

Bug: skia:7192
Change-Id: Ida0551d00f0ac8053a1e0232cfbc4f05c9f35c6c
Reviewed-on: https://skia-review.googlesource.com/65023
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>
1 file changed