cubic-map for non-linear t

Bug: skia:
Change-Id: I248864bd853361c1abfc2d8af61a27ab27a49a91
Reviewed-on: https://skia-review.googlesource.com/38882
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed