encode F16/F32 .pngs as Rec2020

This lets us see more of the range of configs like esrgb.

Change-Id: Id8fe3d6d7545b139d905e4a0e587228c85159043
Reviewed-on: https://skia-review.googlesource.com/154380
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed