This is a reland of 4dac9872

Original change's description:
> Ship globalThis 🎉
>
> Proposal repository:
> https://github.com/tc39/proposal-global
>
> Intent to ship:
> https://groups.google.com/d/msg/v8-users/Vkoh0wXRwaM/Yt7MpzhkAgAJ
>
> Bug: v8:5537
> Change-Id: I60a6c5375165d89548db12fef454a64137d04c27
> Reviewed-on: https://chromium-review.googlesource.com/1195494
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
> Commit-Queue: Mathias Bynens <mathias@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55543}

TBR=adamk@chromium.org,machenbach@chromium.org,gsathya@chromium.org,mathias@chromium.org

No-Presubmit: true
Bug: v8:5537
Change-Id: I1e20d606bb027d7afca713ffde87e183b6f610bd
Reviewed-on: https://chromium-review.googlesource.com/1208633Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55732}