Direct fit of small tables can produce "kBad" transfer functions

Example profile generates a negative 'a' by allowing linear fit for the
for first N-1 points, then a negative slope to the last point.

Bug: oss-fuzz:19467
Change-Id: Ia6a061cdf1c249eeb9d0ef378f89a13a302a1b8d
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/260036
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
4 files changed