This reverts commit c280e7d4.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> [heap] Clear the memory of pooled pages when allocating from the pool.
>
> Bug: chromium:999634
> Change-Id: Ia7a0dd6ddc2477a7656a26548e9a247470d9143f
> Reviewed-on: https://chromium-review.googlesource.com/1041688
> Commit-Queue: Hannes Payer <hpayer@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52948}

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

Change-Id: I838d5fe1e6c6ac8b726a90a44b2eacbea9057866
Reviewed-on: https://chromium-review.googlesource.com/1054070
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53119}