Respect FPArgs local matrix when picking a filtering mode in image shader

Includes a GM that previously drew bilerp, now draws bicubic.

Change-Id: I5e39e8adb49057b57729d9eb9748911ee8584401
Reviewed-on: https://skia-review.googlesource.com/107280
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed