Fixed issue with some A2B0 images being too dark

Fixed issue with some A2B0 images being too dark

The issue was with the A2B0 matrix not being scaled by its encoding
factor when it needed to be (for A2B0 matrices only).

NOTRY=true
NOTREECHECKS=true

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5003

Change-Id: I3f202323e137e1b014e564bd96d87c601c4748ab
Reviewed-on: https://skia-review.googlesource.com/5003
Commit-Queue: Robert Aftias <raftias@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-on: https://skia-review.googlesource.com/5110