Fix textblobrandomfont GM in F16 configs

We were trying to mix the canvas' color space (linear gamma) with N32
color type, which isn't allowed. Propagate the original color type, too.

BUG=skia:

Change-Id: I606b25e690486abe042d6a4b6dda606ac85b546b
Reviewed-on: https://skia-review.googlesource.com/5509
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1 file changed