add tests for cubicmap

check for some special cases:
- degenerate or simple cubic
- 0/0

Bug: skia:
Change-Id: Ie978caf9d862755d9693768695bf84eff9ec80e4
Reviewed-on: https://skia-review.googlesource.com/147112
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Auto-Submit: Mike Reed <reed@google.com>
4 files changed