This reverts commit 0a9d5150.

Reason for revert: another gc-stress failure

Original change's description:
> Reland^2 "[heap] Add mechanism for tracking invalidated slots per memory chunk."
> 
> This reverts commit 6fde541d.
> 
> Bug: chromium:694255
> Change-Id: I4670d0de3d2749afbb3bdb8dc5418822a885330c
> Reviewed-on: https://chromium-review.googlesource.com/597850
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47083}

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

Change-Id: Iaabf4586e0297dccb1ab4ef180b6f1eea173273b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:694255
Reviewed-on: https://chromium-review.googlesource.com/598094Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47084}