Go back to using coverage FP in aarecteffect/convexpoly GMs.

Drawing these with a color FP using fillRectWithFP made them harder
to triage.

TBR: michaelludwig@google.com
Change-Id: I97f181e861c1c24bb2224f00901eb470d868f3c4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375059
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
2 files changed