Reland of Use the LookupIterator in SetAccessor (patchset #1 id:1 of https://codereview.chromium.org/1175323004/)

Reason: Didn't break anything

Original issue's description:
> Revert of Use the LookupIterator in SetAccessor (patchset #2 id:20001 of https://codereview.chromium.org/1178673003/)
>
> Reason for revert:
> Blocks reverting of https://codereview.chromium.org/1175973002
>
> Original issue's description:
> > Use the LookupIterator in SetAccessor
> >
> > BUG=v8:4137
> > LOG=n
> >
> > Committed: https://crrev.com/f93276bfe093f576595c5dcac69cf8f9163915d9
> > Cr-Commit-Position: refs/heads/master@{#28955}
>
> TBR=jkummerow@chromium.org,verwaest@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=v8:4137
>
> Committed: https://crrev.com/11dbd29de57b290ee8dac2a782a53f879beb416f
> Cr-Commit-Position: refs/heads/master@{#28956}

TBR=jkummerow@chromium.org,ishell@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4137

Review URL: https://codereview.chromium.org/1181813002

Cr-Commit-Position: refs/heads/master@{#28967}