Explicitly check edge count >= 2 in non-debug build

We also preserve the check in debug mode that the
count should never be 1 when the path is convex.

Bug: skia:6684
Change-Id: I4d4c9ad9f9d704e94bbe51f10a96f8b3066afaa1
Reviewed-on: https://skia-review.googlesource.com/17983
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Mike Reed <reed@google.com>
4 files changed