Linux sandbox: restrict {get,set}priority in NaCl and renderers.

Linux sandbox: restrict {get,set}priority in NaCl and renderers.

In NaCl processes and renderers, getpriority and setpriority are now
only allowed if they are using PRIO_PROCESS and |who| is either
the current process or 0.

BUG=399473
Committed: https://crrev.com/ae158f413c703c2f60665ba28f078216ec47ad50
Cr-Commit-Position: refs/heads/master@{#294535}

[jln (very slow on Chromium), 2014-09-11 17:57:18]

jln@chromium.org changed reviewers:
+ mseaborn@chromium.org

[jln (very slow on Chromium), 2014-09-11 17:57:24]

Mark: PTAL!

[Mark Seaborn, 2014-09-12 00:10:29]

LGTM

[jln (very slow on Chromium), 2014-09-12 00:15:29]

The CQ bit was checked by jln@chromium.org

[commit-bot: I haz the power, 2014-09-12 00:45:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/552013006/60001

[commit-bot: I haz the power, 2014-09-12 02:47:20]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-12 02:47:21]

Exceeded time limit waiting for builds to trigger.

[jln (very slow on Chromium), 2014-09-12 02:59:21]

The CQ bit was checked by jln@chromium.org

[commit-bot: I haz the power, 2014-09-12 02:59:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/552013006/60001

[commit-bot: I haz the power, 2014-09-12 03:31:58]

Committed patchset #4 (id:60001) as f3d9f9d33e9c7ff19d90386a062c25f2b6dfec96

[commit-bot: I haz the power, 2014-09-12 03:35:49]

Patchset 4 (id:??) landed as
https://crrev.com/ae158f413c703c2f60665ba28f078216ec47ad50
Cr-Commit-Position: refs/heads/master@{#294535}