Revert of [heap] Simplify marking of JSFunction and SFI (patchset #3 id:40001 of https://codereview.chromium.org/2389183002/ )

Reason for revert:
Broke GCStress.

Original issue's description:
> [heap] Simplify marking of JSFunction and SFI
>
> BUG=chromium:651828
>
> Committed: https://crrev.com/4d45ed4597d537cf9624cb6683dc4bd646d11242
> Cr-Commit-Position: refs/heads/master@{#39975}

TBR=hpayer@chromium.org,mlippautz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:651828

Review-Url: https://codereview.chromium.org/2389963007
Cr-Commit-Position: refs/heads/master@{#39983}