Revert of Fix PartitionAlloc randomization on 32-bit systems

Revert of Fix PartitionAlloc randomization on 32-bit systems (patchset #8 id:190001 of https://codereview.chromium.org/1383153002/ )

Reason for revert:
This CL broke TSan bots, see https://crbug.com/539863

BUG=539863
Original issue's description:
> Fix PartitionAlloc randomization on 32-bit systems
>
> Make PartitionAlloc reduce churn on Windows system allocations, and use less aggressive randomization on 32-bit systems in general.
>
> BUG=538479, 394591
> TBR=jchaffraix@chromium.org
>
> Committed: https://crrev.com/794a0e84c6d07da73b687bda35cea145310d2c76
> Cr-Commit-Position: refs/heads/master@{#352477}

TBR=jchaffraix@chromium.org,jfb@chromium.org,tsepez@chromium.org,haraken@chromium.org,jschuh@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=538479, 394591
Committed: https://crrev.com/1d3a58dbd9215cdb5b052f4f43c85293c9a44dc9
Cr-Commit-Position: refs/heads/master@{#353038}

[Alexander Potapenko, 2015-10-08 12:07:31]

Created Revert of Fix PartitionAlloc randomization on 32-bit systems

[commit-bot: I haz the power, 2015-10-08 12:07:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1397513003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1397513003/1

[commit-bot: I haz the power, 2015-10-08 12:08:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-08 12:09:51]

Patchset 1 (id:??) landed as
https://crrev.com/1d3a58dbd9215cdb5b052f4f43c85293c9a44dc9
Cr-Commit-Position: refs/heads/master@{#353038}

[haraken, 2015-10-08 12:42:39]

LGTM

[jschuh, 2015-10-08 16:02:19]

Retroactive lgtm