Initial checkin of accessibility extensions.

(Re-land) initial checkin of accessibility extensions.

We still need to clean up style violations and add i18n to all of these.

BUG=416983
R=plundblad@chromium.org

Committed: https://crrev.com/faa70371405c5bac4258dda0a7901f76f66f6944
Cr-Commit-Position: refs/heads/master@{#296760}

[dmazzoni, 2014-09-23 21:05:46]

dmazzoni@chromium.org changed reviewers:
+ dtseng@chromium.org, plundblad@chromium.org

[Peter Lundblad, 2014-09-25 15:51:01]

lgtm

Rubberstump, we can work on them when they are checked in.

[dmazzoni, 2014-09-25 17:28:56]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-09-25 17:29:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/593293002/20001

[commit-bot: I haz the power, 2014-09-25 17:39:46]

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

[commit-bot: I haz the power, 2014-09-25 17:39:47]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[commit-bot: I haz the power, 2014-09-25 17:45:56]

Patchset 2 (id:??) landed as
https://crrev.com/6589af684eecffa198c1998bccadfbd362054241
Cr-Commit-Position: refs/heads/master@{#296737}

[dmazzoni, 2014-09-25 17:46:02]

Committed patchset #2 (id:20001) manually as 6589af6 (presubmit successful).

[dmazzoni, 2014-09-25 19:24:37]

Committed patchset #3 (id:40001) manually as faa7037 (presubmit successful).

[commit-bot: I haz the power, 2014-09-25 19:24:39]

Patchset 3 (id:??) landed as
https://crrev.com/faa70371405c5bac4258dda0a7901f76f66f6944
Cr-Commit-Position: refs/heads/master@{#296760}