Update comment on isNumericalTransferFn to clarify that fn is always set

Change-Id: I7902e4355999f31bf92aa8294a2c1a32840249c2
Bug: chromium:960620
Change-Id: I7902e4355999f31bf92aa8294a2c1a32840249c2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/252479
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed