Let test_isolation_mode default to check on mac.

Let test_isolation_mode default to check on mac.

It was set to noop in https://chromiumcodereview.appspot.com/14055005 due to
issues with xcode. Now that xcode is no longer used, it can be set to check
again.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=238025

R=maruel@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=241681

[Nico, 2013-11-27 22:37:25]

hooray?

[Nico, 2013-11-30 22:35:09]

ping

[M-A Ruel, 2013-12-02 00:02:41]

lgtm, sorry for the delay.

[commit-bot: I haz the power, 2013-12-02 01:36:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/92303002/1

[commit-bot: I haz the power, 2013-12-02 04:28:38]

Change committed as 238025

[commit-bot: I haz the power, 2013-12-18 21:07:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/92303002/1

[Nico, 2013-12-18 22:19:37]

Committed patchset #1 manually as r241681 (presubmit successful).

[Vadim Sh., 2013-12-19 00:25:09]

A revert of this CL has been created in
https://codereview.chromium.org/110693005/ by vadimsh@chromium.org.

The reason for reverting is: Broke Google Chrome Mac builder.