Add epsilon to linear gradient

Related bug in Ganesh: https://crbug.com/40616713

Change-Id: I8f50660ece8ddcb420d27f5cfaa60190d6bbb12a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/864156
Reviewed-by: James Godfrey-Kittle <jamesgk@google.com>
Commit-Queue: Nathan Sanchez <nathanasanchez@google.com>
3 files changed