This reverts commit d4a742fd.

Reason for revert: gc-stress failures

Original change's description:
> Reland "[heap] Add mechanism for tracking invalidated slots per memory chunk."
> 
> 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/596868
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47068}

TBR=ulan@chromium.org,mlippautz@chromium.org

Change-Id: I81c6059a092cc5834acd799c51fd30dc0ecf5b27
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:694255
Reviewed-on: https://chromium-review.googlesource.com/597787Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47078}