Revert "Revert "Take missed opportunity: memset for A8.""

Revert "Revert "Take missed opportunity: memset for A8.""

This reverts commit 2028625f9b92b3423d841a926f785140a8955a84.

Reason for revert: not the reason for broken roll.

Original change's description:
> Revert "Take missed opportunity: memset for A8."
>
> This reverts commit 9cee33e631679fc8195e7892b5aa5fdffb0b568e.
>
> Reason for revert: Chrome roll?
>
> Original change's description:
> > Take missed opportunity: memset for A8.
> >
> > Just recently noticed we weren't doing this.
> > It seems to be triggering all the time.
> >
> > Draws the same of course.
> >
> > Change-Id: Ie3d869a05194a5d52d635643eba1c96c8a21ce67
> > Reviewed-on: https://skia-review.googlesource.com/8471
> > Reviewed-by: Mike Reed <reed@google.com>
> > Commit-Queue: Mike Klein <mtklein@chromium.org>
> >
>
> TBR=mtklein@chromium.org,msarett@google.com,reed@google.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Change-Id: I26a3f2b1a9ae9093180e9c5cc61094b239377c17
> Reviewed-on: https://skia-review.googlesource.com/8606
> Reviewed-by: Mike Klein <mtklein@chromium.org>
> Commit-Queue: Mike Klein <mtklein@chromium.org>
>

TBR=mtklein@chromium.org,msarett@google.com,reed@google.com
NOPRESUBMIT=true

Change-Id: Ib14360c6669abf9dd0c5bd152773b314d094fe72
Reviewed-on: https://skia-review.googlesource.com/8617
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>