This reverts commit be2f237d.

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: I9d70037dda612528368fb1ba330dc6f6510a14a6
Reviewed-on: https://chromium-review.googlesource.com/1055450Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53129}