sandbox: run Credentials.CanDetectRoot as a SANDBOX_TEST

sandbox: run Credentials.CanDetectRoot as a SANDBOX_TEST

This test calls chdir() which corrupts subsequent tests like
NamespaceSandboxTest.

TBR=jln@chromium.org

Committed: https://crrev.com/f90ebdf89f1fb8c2b8e5e54f5cbdb1846281d360
Cr-Commit-Position: refs/heads/master@{#314530}

[mdempsky, 2015-02-04 08:05:42]

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

[rickyz (no longer on Chrome), 2015-02-04 08:07:22]

lgtm

Thanks for catching this

[mdempsky, 2015-02-04 08:09:49]

The CQ bit was checked by mdempsky@chromium.org

[mdempsky, 2015-02-04 08:09:56]

On 2015/02/04 08:07:22, rickyz wrote:
> lgtm
> 
> Thanks for catching this

Thanks for the quick review. :)

[commit-bot: I haz the power, 2015-02-04 08:10:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/902533002/1

[commit-bot: I haz the power, 2015-02-04 08:10:25]

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

[commit-bot: I haz the power, 2015-02-04 08:10:26]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[mdempsky, 2015-02-04 09:27:11]

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

[mdempsky, 2015-02-04 09:27:18]

The CQ bit was checked by mdempsky@chromium.org

[commit-bot: I haz the power, 2015-02-04 09:27:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/902533002/1

[mdempsky, 2015-02-04 09:29:53]

jln: TBR'ing you to appease commit-bot.

[commit-bot: I haz the power, 2015-02-04 09:30:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-04 09:32:09]

Patchset 1 (id:??) landed as
https://crrev.com/f90ebdf89f1fb8c2b8e5e54f5cbdb1846281d360
Cr-Commit-Position: refs/heads/master@{#314530}

[jln (very slow on Chromium), 2015-02-04 23:24:28]

https://codereview.chromium.org/902533002/diff/1/sandbox/linux/services/crede...
File sandbox/linux/services/credentials_unittest.cc (right):

https://codereview.chromium.org/902533002/diff/1/sandbox/linux/services/crede...
sandbox/linux/services/credentials_unittest.cc:127: PCHECK(0 ==
chdir("/proc/"));
Note: we have SANDBOX_ASSERT_EQ() etc for these. (But this prints errno so,
good.)