Add GM test slide to reproduce Perlin noise issue.

This issue only happens on certain GPUs--let's see if we can get it
to occur in our testing lab.

Bug: skia:14411
Change-Id: I13da36fbc91ce41e5cad711c4b003d7a88fc95f1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/717816
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed