Add antialiasing to SkDropShadowImageFilter's shadow draw

A BW draw in the SkDropShadowImageFilter can lead to unexpected popping of the shadow when the dest rect lies on half pixel boundaries.

Change-Id: Ibc59dacc79bca8955981ec2889e79facd7d2de83
Reviewed-on: https://skia-review.googlesource.com/5669
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed