add an ulp of error on the clamp asserts

Change-Id: I3903e266e2e99ceab647fbc45c764e3526e600af
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/275198
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed