use new cubic code for old cubics

Change-Id: Id1926ce12106644a90ce15c9b537d6a4d4f2419a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/305384
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed