Add filter param to picture-shader

Bug: skia:7650
Change-Id: I5eb6d73cf92c22b3846d4f4b81c7a8c06e2889a3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/354659
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
5 files changed