Disable BootstrapSandbox on Mac.

Disable BootstrapSandbox on Mac.

Disable BootstrapSandbox on Mac, because of an issue where the
constructor is called on the wrong thread.

BUG=501128
Committed: https://crrev.com/f1118ad1db53d8ec6be1f24afec3b03d96c01037
Cr-Commit-Position: refs/heads/master@{#334823}

[Will Harris, 2015-06-16 23:00:13]

wfh@chromium.org changed reviewers:
+ rsesek@chromium.org

[Will Harris, 2015-06-16 23:00:51]

rsesek - once I get an l-g-t-m from you I'll hopefully find an owner... :)

[Robert Sesek, 2015-06-16 23:01:33]

LGTM

[Will Harris, 2015-06-16 23:01:58]

wfh@chromium.org changed reviewers:
+ nick@chromium.org

[Will Harris, 2015-06-16 23:02:08]

nick - PTAL

[ncarter (slow), 2015-06-17 05:47:33]

lgtm

[Will Harris, 2015-06-17 10:54:08]

The CQ bit was checked by wfh@chromium.org

[commit-bot: I haz the power, 2015-06-17 10:54:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1189823003/1

[commit-bot: I haz the power, 2015-06-17 12:09:24]

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

[commit-bot: I haz the power, 2015-06-17 12:09:25]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Will Harris, 2015-06-17 13:19:51]

The CQ bit was checked by wfh@chromium.org

[commit-bot: I haz the power, 2015-06-17 13:20:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1189823003/1

[commit-bot: I haz the power, 2015-06-17 14:11:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-17 14:12:24]

Patchset 1 (id:??) landed as
https://crrev.com/f1118ad1db53d8ec6be1f24afec3b03d96c01037
Cr-Commit-Position: refs/heads/master@{#334823}