detect bad conic weights

Bug: skia:7478
Change-Id: I5fb254e10f3f38184fe41eb01e543f04b1a03081
Reviewed-on: https://skia-review.googlesource.com/92641
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed