Expand powerless hue gradient testing

Covers all four polar color spaces, and adds additional test cases.

Bug: chromium:1462612
Change-Id: Ib646910d4f318b9ec93217f01529257c1e47e76d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/771697
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed