Revert of add backdrop option to SaveLayerRec (patchset #14 id:260001 of https:/...

Revert of add backdrop option to SaveLayerRec (patchset #14 id:260001 of https://codereview.chromium.org/1523053003/ )

Reason for revert:
serialized != direct, will investigate

Original issue's description:
> add backdrop option to SaveLayerRec
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1523053003
>
> Committed: https://skia.googlesource.com/skia/+/247415969a9a5ed6c83cc09395472416c4b7de7f

TBR=robertphillips@google.com,bsalomon@google.com,mtklein@google.com
# 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/1565203002