Guard against integer overflow when classifying transfer functions

Bug: chromium:1016183
Change-Id: I9ad5a18a5941661dbd88963d70a043cbe5dcc470
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/251245
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed