Revert of Only use FreeSpace objects in the free list.

Revert of Only use FreeSpace objects in the free list. (patchset #3 id:40001 of https://codereview.chromium.org/876613002/)

Reason for revert:
Test failures

Original issue's description:
> Only use FreeSpace objects in the free list.
>
> This solves an issue with the custom startup snapshot, in cases where
> deserializing the isolate requires more than one page per space.
>
> R=hpayer@chromium.org
>
> Committed: https://crrev.com/66964395108f03220cb6f45ddc73c5965e2c76a9
> Cr-Commit-Position: refs/heads/master@{#26285}

TBR=hpayer@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/cc79418b598615bc00ebbbe81acb50a1da56ae8f
Cr-Commit-Position: refs/heads/master@{#26287}

[Yang, 2015-01-27 09:40:35]

Created Revert of Only use FreeSpace objects in the free list.

[commit-bot: I haz the power, 2015-01-27 09:41:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/882443004/1

[commit-bot: I haz the power, 2015-01-27 09:41:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-27 09:41:28]

Patchset 1 (id:??) landed as
https://crrev.com/cc79418b598615bc00ebbbe81acb50a1da56ae8f
Cr-Commit-Position: refs/heads/master@{#26287}