Reason for revert:
Field representation is not preserved
Original issue's description:
> [turbofan] Set proper representation for initial arguments length.
>
> The JSArgumentsObject::length representation is initially Smi, so we can
> record that on the initial map and use it to optimize the accesses in
> TurboFan based on that. Similar for JSSloppyArgumentsObject::caller.
>
> BUG=v8:6262
> R=yangguo@chromium.org
>
> Review-Url: https://codereview.chromium.org/2810333004
> Cr-Commit-Position: refs/heads/master@{#44644}
> Committed: 5eec7df9b3TBR=yangguo@chromium.org,bmeurer@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=v8:6262
Review-Url: https://codereview.chromium.org/2825323002
Cr-Commit-Position: refs/heads/master@{#44893}
6b4b062489