Transform verts using nonsquare matrices when available.

We were previously doing a square-matrix multiply then discarding one
third of the result; now, when available, we just get the result we need
via a non-square multiply.

Change-Id: Ie13ae6f2c7f23e3a4c1f2c4eeb6361a97cdccf67
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/403079
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
3 files changed