Improve quadratic evaluation at t

Use fma to preserve the precision between terms.

Bug: skia:14252
Change-Id: I11e97e769c827673204be3e8ba1e099194f9db0e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/708119
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed