This reverts commit c59b81d7.

Original change's description:
> [heap] Add mechanism for tracking invalidated slots per memory chunk.

> For correct slots recording in concurrent marker, we need to resolve
> the race that happens when
> 1) the mutator is invalidating slots for double unboxing or string
> conversions
> 2) and the concurrent marker is recording these slots.

> This patch adds a data-structure for tracking the invalidated objects.
> Thus we can allow the concurrent marker to record slots without
> worrying about clearing them. During old-to-old pointer updating phase
> we re-check all slots that belong to the invalidated objects.

BUG=chromium:694255

Change-Id: Idf8927d162377a7bbdff34f81a87e52db27d6a9f
Reviewed-on: https://chromium-review.googlesource.com/596868Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47068}