Revert of fix uninit immediate mode member var in GrDrawingManager (patchset #1 id...

Revert of fix uninit immediate mode member var in GrDrawingManager (patchset #1 id:1 of https://codereview.chromium.org/2312333002/ )

Reason for revert:
Reverting in order to revert earlier CL

Original issue's description:
> fix uninit immediate mode member var in GrDrawingManager
>
> TBR=robertphillips@google.com
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2312333002
>
> NOTRY=true
>
> Committed: https://skia.googlesource.com/skia/+/ce3b852529ad1f026aad3976f3213c8943554ba2

TBR=robertphillips@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2311243003