This reverts commit 5b434929.

Changes after the original CL:
- Right-trimming registers the array as an object with invalidated
  slots.
- Left-trimming moves the array start in the invalidated slots map.

Original change's description:
> Fix invalidation of old-to-old slots after object trimming.
>
> A recorded old-to-old slot may be overwritten with a pointer to a new
> space object. If the object containing the slot is trimmed later on,
> then the mark-compactor may crash on a stale pointer to new space.
>
> This patch ensures that:
> 1) On trimming of an object we add it to the invalidated_slots sets.
> 2) The InvalidatedSlotsFilter::IsValid returns false for slots outside
>    the invalidated object unless the page was already swept.
>
> Array left-trimming is handled as a special case because object start
> moves and cannot be added to the invalidated set. Instead, we clear
> the freed memory so that the recorded slots contain Smi values.
>
> Bug: chromium:870226,chromium:816426
> Change-Id: Iffc05a58fcf52ece45fdb085b5d1fd4b3acb5d53
> Reviewed-on: https://chromium-review.googlesource.com/1163784
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54953}

Change-Id: I1f1080f680196c581f62aef8d3a00a595f9bb9b0
Reviewed-on: https://chromium-review.googlesource.com/1165555
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55066}