fix pathops handling of tiny wrapback quads and cubics

If a quad or cubic reverses on itself, path ops breaks
it in two. It determines the type of curve remaining,
but needs to replace near-zero with zero first.

TBR=reed@google.com
Bug:790731
Change-Id: I3a1afa14fff064ca874b5abc768ec1ec5c2cf22f
Reviewed-on: https://skia-review.googlesource.com/79400
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Cary Clark <caryclark@skia.org>
3 files changed