only tweak sampling when hitting pixel centers

I think this was the rough idea?  I'm a little fuzzy
on the SkMatrixProvider overloads that concat... I
really don't have a head for matrix transforms.

Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Bug: skia:11260
Change-Id: I6eb8e4397da035d17fe6b96e5c5494dce0483e26
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/365520
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
4 files changed