Add namespace sandbox to about page.

Add namespace sandbox to about page.

This unindents the lines about PID/network namespaces, since those now apply to both the setuid or unprivileged namespace sandbox.

This is a resubmit of https://codereview.chromium.org/873283004/

TBR=jhawkins@chromium.org
BUG=312380
Committed: https://crrev.com/e1274d29f116c9eba6bc3d16d2b5d53a77b99a9a
Cr-Commit-Position: refs/heads/master@{#315945}

[rickyz (no longer on Chrome), 2015-02-12 01:13:33]

Patchset #1 (id:1) has been deleted

[rickyz (no longer on Chrome), 2015-02-12 02:09:02]

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

[rickyz (no longer on Chrome), 2015-02-12 02:09:03]

Here's a resend of the sandbox about page change. I plan to submit this after

1) issue 915243002 is submitted
2) The cros test update is submitted and this runs cleanly on one of PFQs that
failed previously

[jln (very slow on Chromium), 2015-02-12 03:11:32]

lgtm

Add in the commit message that this is a re-send of https://.... and you can TBR
the previous owner for the about_ui changes.

[jln (very slow on Chromium), 2015-02-12 03:11:59]

Did you figure out on which bots
chrome/test/data/webui/sandboxstatus_browsertest.js run these days? I didn't
look yet, but they don't run on CQ anymore, correct?

[rickyz (no longer on Chrome), 2015-02-12 04:02:36]

New patchsets have been uploaded after l-g-t-m from jln@chromium.org

[rickyz (no longer on Chrome), 2015-02-12 04:05:00]

On 2015/02/12 03:11:59, jln wrote:
> Did you figure out on which bots
> chrome/test/data/webui/sandboxstatus_browsertest.js run these days? I didn't
> look yet, but they don't run on CQ anymore, correct?

This should be run under browser_tests - my suspicion is that the bots running
it don't support user namespaces, but I need to double check this. Will TBR this
once a cros pfq trybot succeeds.

[rickyz (no longer on Chrome), 2015-02-12 08:17:19]

rickyz@chromium.org changed reviewers:
+ jhawkins@chromium.org

[rickyz (no longer on Chrome), 2015-02-12 08:17:27]

The CQ bit was checked by rickyz@chromium.org

[commit-bot: I haz the power, 2015-02-12 08:17:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/916153003/60001

[commit-bot: I haz the power, 2015-02-12 08:31:05]

Committed patchset #3 (id:60001)

[commit-bot: I haz the power, 2015-02-12 08:31:52]

Patchset 3 (id:??) landed as
https://crrev.com/e1274d29f116c9eba6bc3d16d2b5d53a77b99a9a
Cr-Commit-Position: refs/heads/master@{#315945}