mac: Fix BookmarkBarControllerTest.TestClearOnDealloc on Yosemite.

mac: Fix BookmarkBarControllerTest.TestClearOnDealloc on Yosemite.

In Yosemite, the owner of a nib file is retain/autoreleased during the
initialization of the nib. I wrapped the constructor of the
BookmarkBarController in an @autoreleasepool block to allow the test to control
the destruction timing of the BookmarkBarController.

BUG=390276
Committed: https://crrev.com/1124df6b0a9a980605f8ce342bf1a49403656a84
Cr-Commit-Position: refs/heads/master@{#300312}

[erikchen, 2014-10-17 23:03:06]

Patchset #1 (id:1) has been deleted

[erikchen, 2014-10-17 23:03:29]

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

[erikchen, 2014-10-17 23:03:29]

rsesek: Please review.

[Robert Sesek, 2014-10-20 15:10:45]

LGTM

[erikchen, 2014-10-20 18:12:28]

The CQ bit was checked by erikchen@chromium.org

[commit-bot: I haz the power, 2014-10-20 18:13:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/660063004/20001

[commit-bot: I haz the power, 2014-10-20 19:22:38]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2014-10-20 19:23:14]

Patchset 1 (id:??) landed as
https://crrev.com/1124df6b0a9a980605f8ce342bf1a49403656a84
Cr-Commit-Position: refs/heads/master@{#300312}