SkMatrixProvider: Move local-to-device storage to base class

Simplifies all the helpers. Also changed "override" to "post-concat", to
reflect what it's really doing (because we're going to need post-concat
soon anyway).

Change-Id: Iff388998407441c8df418a3c8464eb8f6aad0786
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289197
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
4 files changed