support 16161616 in fm

Everything was pretty much already plumbed through using
SkRasterPipeline, with a few key connections made here.

This support is mostly useful for differentially debugging my CLs
stacked on top of it.

Change-Id: I9c2f2ea6cd8890c057890409f21c7698857c599a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/303651
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
4 files changed