Add a color-spin control to Viewer

This cycles the primaries, just like SkColorSpace::makeColorSpin.
Helpful for debugging more exotic color space issues.

Change-Id: I3434c7a9f24642f13be0ac3513599a15247d1f6f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/469360
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
1 file changed