detect (and preserve) if patch colors are opaque

Bug: skia:
Change-Id: Ida3a1ff3f78db2498a6dfc655d8be4de8ad912c7
Reviewed-on: https://skia-review.googlesource.com/17380
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed