Increase precision of equality checking for color space transfer fns

BUG=skia:

Change-Id: I7b921d34539c071e63a47fb7151dc1dcdaa08cb3
Reviewed-on: https://skia-review.googlesource.com/9636
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed