Fix a failure in test_api.js when accessibility auditing is not enabled.

Fix a failure in test_api.js when accessibility auditing is not enabled.

Tests that don't enable auditing generate a confusing stack trace and
a setUp method that would call its base method by virtue of good practice
will not work.

BUG=458910
Committed: https://crrev.com/04fde03c302535b6d52da89d5c8c1cd0dac11d2e
Cr-Commit-Position: refs/heads/master@{#316570}

[Paweł Hajdan Jr., 2015-02-16 15:16:04]

Please get this reviewed by someone working on accessibility. My stamp for
chrome/test/data shouldn't even be needed.

[Peter Lundblad, 2015-02-16 15:35:10]

plundblad@chromium.org changed reviewers:
+ dbeam@chromium.org
- phajdan.jr@chromium.org

[Peter Lundblad, 2015-02-16 15:35:10]

Changing reviewer to Dan.

[Dan Beam, 2015-02-17 06:48:06]

lgtm, though window.axs is mildly preferred

[Peter Lundblad, 2015-02-17 10:17:42]

New patchsets have been uploaded after l-g-t-m from dbeam@chromium.org

[Peter Lundblad, 2015-02-17 13:56:25]

The CQ bit was checked by plundblad@chromium.org

[commit-bot: I haz the power, 2015-02-17 13:57:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/927083003/60001

[commit-bot: I haz the power, 2015-02-17 14:00:28]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-02-17 14:01:13]

Patchset 4 (id:??) landed as
https://crrev.com/04fde03c302535b6d52da89d5c8c1cd0dac11d2e
Cr-Commit-Position: refs/heads/master@{#316570}