Handle dl role for browsertests

Handle dl role for browsertests
This patch enables AccessibilitDl test and adds the case for dl role in
browsertests on Mac and Android.

BUG=226505
R=dmazzoni@chromium.org, aboxhall@chromium.org

Committed: https://crrev.com/4c5b538078c55a046de21033e3fef61cfa4e7aa2
Cr-Commit-Position: refs/heads/master@{#298013}

[je_julie(Not used), 2014-10-03 05:20:44]

je_julie.kim@samsung.com changed reviewers:
+ aboxhall@chromium.org

[je_julie(Not used), 2014-10-03 05:23:18]

Dominic, PTAL.

[dmazzoni, 2014-10-03 05:50:22]

lgtm

[je_julie(Not used), 2014-10-03 07:41:34]

The CQ bit was checked by je_julie.kim@samsung.com

[commit-bot: I haz the power, 2014-10-03 07:42:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/627603002/1

[commit-bot: I haz the power, 2014-10-03 08:35:08]

Committed patchset #1 (id:1) as 558f3937f0696879ca8ba61a5e072fd0dfa7bb85

[commit-bot: I haz the power, 2014-10-03 08:35:49]

Patchset 1 (id:??) landed as
https://crrev.com/4c5b538078c55a046de21033e3fef61cfa4e7aa2
Cr-Commit-Position: refs/heads/master@{#298013}