This reverts commit 0bf9c60c.

Reason for revert: breaks minor_mc bot

Original change's description:
> [heap] Unprotect code pages on demand in MinorMC
> 
> This reduces average pause of MinorMC in Richards benchmark from 0.32ms
> to 0.25ms:
> 
> baseline pause
>   len: 22
>   min: 0.3
>   max: 0.6
>   avg: 0.322727272727
>   [0,5[: 22
> 
> pause
>   len: 22
>   min: 0.2
>   max: 0.7
>   avg: 0.254545454545
>   [0,5[: 22
> 
> Bug: chromium:651354
> Change-Id: I701ca800d7c6986534d1de2e3051476e91a88d7d
> Reviewed-on: https://chromium-review.googlesource.com/1055507
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#53125}

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

Change-Id: Ib227e37fa60d608f94c3111a9b431baf0f488790
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:651354
Reviewed-on: https://chromium-review.googlesource.com/1053970Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53127}