Revert of Introduce LookupIterator::Restart() and use it (patchset #2 id:20001 of https://codereview.chromium.org/1416053007/ )

Reason for revert:
Breaks test if rolled into Chromium: http://build.chromium.org/p/chromium.win/buildstatus?builder=Vista%20Tests%20%281%29&number=60441

Needed so the reverts applies cleanly and seems to be related to the offending CL.

Original issue's description:
> Introduce LookupIterator::Restart() and use it
>
> Committed: https://crrev.com/5676415b4add059b78f98a9a762d00c8d721dbcd
> Cr-Commit-Position: refs/heads/master@{#31483}

TBR=verwaest@chromium.org,jkummerow@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1418213003

Cr-Commit-Position: refs/heads/master@{#31534}