Add several more unit tests of runtime effects

Did some cleanup to remove repetition that was distracting from the
thing being tested.

Change-Id: Ie385c6ec2d1325a1bd0ba5c2270e7f2ddd1d24b2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/305076
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
1 file changed