Add new GM to demonstrates SkGaussianEdgeShader

This would've caught the incorrect distances in the center bug

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3111

Change-Id: I9461a8865b561cc139a18a5e779e933d7979ee0d
Reviewed-on: https://skia-review.googlesource.com/3111
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
1 file changed