Avoid interpolating color lut with less than 2 points

Bug: 717935
Change-Id: Ibf15b815891eef5a0239bc408bcbfe7c8b1507c5
Reviewed-on: https://skia-review.googlesource.com/15301
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
1 file changed