Add Tests for SkGeometry::ChopMonoCubicAt

Change-Id: I2365ff78e2ed5dfa8a9075a879af363dc9d8b84a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/620224
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
4 files changed