Create hardstop_gradients_many test slide.

This GM presents different gradients with an increasing number of
hardstops, from 1 to 100.

Change-Id: I1c279c6ea1a25f9785001aa29db632547a38ab68
Bug: skia:8401
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/457437
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2 files changed