This was only being used in one effect (and for no good reason). SkSL is
plenty powerful to re-implement something similar if required, at no
real performance cost.
Re-implemented the one effect that used it with simpler math in the
script, updated the copy of that effect in the gallery.
Docs-Preview: https://skia.org/?cl=247040
Change-Id: I68c86d6550dd4f003f6ba5ecd0febab37b86540b
Bug: skia:9513
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/247040
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
7edfb69406