Revert of Delete SkFlattenable::Type (part 1) (patchset #1 id:1 of https://codereview.chromium.org/1861013002/ )

Reason for revert:
See sugoi's comment.

Original issue's description:
> Delete SkFlattenable::Type (part 1)
>
> This should allow me to delete uses of SkFlattenable::Type in Chrome.
> Then I'll follow up with the full delete.
> https://codereview.chromium.org/1834303003/
>
> TBR=reed@google.com
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1861013002
>
> Committed: https://skia.googlesource.com/skia/+/6b63536e917d86028630199c4eef4aa1597292ce

TBR=reed@google.com,mtklein@google.com,sugoi@chromium.org,senorblanco@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1860693005