helper api to force a raster image

Bug: skia:
Change-Id: I53f3d426e97f446b17dc965fa8dd6d6aae441ac9
Reviewed-on: https://skia-review.googlesource.com/79901
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed