Fix Mac sandbox meta data access

Fix Mac sandbox meta data access

Sandbox::AllowMetadataForPath() currently allow all metadata access due to
https://codereview.chromium.org/10539009/ made the for loop comparison
in Sandbox::AllowMetadataForPath() always false, when we actually only
want to allow access to the path and all its parent path until root.

Turn the for loop to a do/while loop instead as it's a better fit, also
add a test case for Sandbox::AllowMetadataForPath().

It should only affect component builds on OS X 10.6 and utility process
as no other process is using this mechanism.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289526

[Nico, 2014-08-13 16:08:00]

lgtm, thanks!

[Avi (use Gerrit), 2014-08-13 16:27:14]

owner drive-by lgtm

[Jiang Jiang, 2014-08-13 17:09:44]

The CQ bit was checked by jiangj@opera.com

[commit-bot: I haz the power, 2014-08-13 17:11:13]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jiangj@opera.com/472513002/1

[commit-bot: I haz the power, 2014-08-14 02:03:09]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_aosp on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)

[commit-bot: I haz the power, 2014-08-14 08:06:38]

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

[commit-bot: I haz the power, 2014-08-14 08:06:38]

Try jobs failed on following builders:
  android_aosp on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)

[Jiang Jiang, 2014-08-14 08:27:09]

The CQ bit was checked by jiangj@opera.com

[commit-bot: I haz the power, 2014-08-14 08:29:10]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jiangj@opera.com/472513002/1

[commit-bot: I haz the power, 2014-08-14 11:25:59]

Committed patchset #1 (1) as 289526