Revert of Revert of SkDrawCommand scrubbing (patchset #1 id:1 of https://codereview.chromium.org/712683002/)

Reason for revert:
Chromium clients updated, this should be canary-proof now.

Original issue's description:
> Revert of SkDrawCommand scrubbing (patchset #2 id:20001 of https://codereview.chromium.org/706363002/)
>
> Reason for revert:
> Canary borkage.
>
> Original issue's description:
> > SkDrawCommand scrubbing
> >
> > Remove unused ctor, constify, etc.
> >
> > R=robertphillips@google.com
> >
> > Committed: https://skia.googlesource.com/skia/+/1931ec5b5dac68f1e452af0c65161bdce35b2dec
>
> TBR=robertphillips@google.com
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://skia.googlesource.com/skia/+/9063ddd511f8e0d8c7454950cbc56e273678bf60

TBR=robertphillips@google.com
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/708333002