simplify GrFPArgs, isolating localmatrix

Bug: skia:
Change-Id: Icee24e0a355a7d1bae29b7721b4d95db8023ca77
Reviewed-on: https://skia-review.googlesource.com/97063
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>
6 files changed