Small refactor around futex.h.

Small refactor around futex.h.

This is the preparation of seccomp-bpf implementation
for nacl_helper_nonsfi.
PNaCl toolchain does not provides linux/futex.h.
This CL is the preparation to reuse android_futex.h
for PNaCl toolchain, too.

TEST=Ran bots.
BUG=358465
Committed: https://crrev.com/3b996212fa3c92af3233246ae54af728eb7c3591
Cr-Commit-Position: refs/heads/master@{#324996}

[hidehiko, 2015-04-10 15:38:13]

hidehiko@chromium.org changed reviewers:
+ mdempsky@chromium.org

[hidehiko, 2015-04-10 15:38:14]

Hi, could you take a look?

Thanks,
- hidehiko

[hidehiko, 2015-04-10 16:55:30]

Patchset #1 (id:1) has been deleted

[mdempsky, 2015-04-13 18:16:18]

lgtm

[hidehiko, 2015-04-14 02:19:57]

The CQ bit was checked by hidehiko@chromium.org

[commit-bot: I haz the power, 2015-04-14 02:20:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1076213002/20001

[commit-bot: I haz the power, 2015-04-14 03:41:23]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-04-14 03:43:12]

Patchset 1 (id:??) landed as
https://crrev.com/3b996212fa3c92af3233246ae54af728eb7c3591
Cr-Commit-Position: refs/heads/master@{#324996}

[dnicoara, 2015-04-15 17:22:26]

A revert of this CL (patchset #1 id:20001) has been created in
https://codereview.chromium.org/1084173003/ by dnicoara@chromium.org.

The reason for reverting is: Breaks ChromeOS veyron_jerry boot.

BUG=477352.