SkPDF:  start to support AlphaOnly Images as masks.

Does not work when img->isAlphaOnly() && pnt.getMaskFilter().

Change-Id: I60712d035e3a505799258e24660bba30f2c0ed53
Reviewed-on: https://skia-review.googlesource.com/22723
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
1 file changed