Premultiply in DM before drawing unpremul f16

We special case N32, but need to also handle f16

Change-Id: I0d6061d55e55c5952c740255e4600366d8d77919
Reviewed-on: https://skia-review.googlesource.com/17786
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed