use GrFPArgs for maskfilters

Bug: skia:
Change-Id: I8516a3b0f6d8301c51f0861c65b9fe8f692fc5e5
Reviewed-on: https://skia-review.googlesource.com/97260
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
6 files changed