This is a reland of e1ad9b89

Original change's description:
> Fixes for size_t LookupIterator
>
> Fixing some fallout from c968607e
> aka r65078
>
> Bug: chromium:1026729,chromium:1026856,chromium:1026909,chromium:1026974
> Change-Id: I98a4466595fbf1635af403ab58842977882c0453
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1930907
> Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#65158}

Tbr: verwaest@chromium.org,mstarzinger@chromium.org
Bug: chromium:1026729, chromium:1026856, chromium:1026909, chromium:1026974
Change-Id: I66695f05c4910c46f3c75209e14135075721f2cf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1932839Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65162}