Reland of [heap] Remove eager shortcut in JSFunction visitor. (patchset #1 id:1 of https://codereview.chromium.org/1488063002/ )

Reason for revert:
Suspect for crashing found, relanding for canary coverage.

Original issue's description:
> Revert of [heap] Remove eager shortcut in JSFunction visitor. (patchset #1 id:1 of https://codereview.chromium.org/1476223002/ )
>
> Reason for revert:
> Still investigating bad canary.
>
> Original issue's description:
> > [heap] Remove eager shortcut in JSFunction visitor.
> >
> > This removes an optimization in the static JSFunction visitor that
> > eagerly marked through to the SharedFunctionInfo for code flushing
> > candidates. This causes all processing in VisitJSFunction to be
> > side-stepped and hence might cause leaks.
> >
> > R=hpayer@chromium.org
> >
> > Committed: https://crrev.com/a29f0576c32e8fda90bf7ab19c6d170568150a7f
> > Cr-Commit-Position: refs/heads/master@{#32332}
>
> TBR=mstarzinger@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://crrev.com/672b49119b857c4f96234b03e48b4b60de256969
> Cr-Commit-Position: refs/heads/master@{#32463}

TBR=mstarzinger@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1486413006

Cr-Commit-Position: refs/heads/master@{#32554}