Revert of [Mac] Enter should trigger the buttons in the new avatar bubble.

Revert of [Mac] Enter should trigger the buttons in the new avatar bubble. (patchset #1 id:1 of https://codereview.chromium.org/644023002/)

Reason for revert:
This doesn't do what it's supposed to do, and after more discussions with groby@, Enter is really only used for default buttons on Mac, not all buttons.

Original issue's description:
> [Mac] Enter should trigger the buttons in the new avatar bubble.
>
> Only space seems to work by default.
>
> BUG=415823
>
> Committed: https://crrev.com/9750bbaa9e0b3d0bbe44431216d570ecc789024f
> Cr-Commit-Position: refs/heads/master@{#299157}

TBR=groby@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=415823
Committed: https://crrev.com/4530a109e1867a9662ea92a3048e3db5e02dbd60
Cr-Commit-Position: refs/heads/master@{#300175}

[noms (inactive), 2014-10-17 22:18:58]

Created Revert of [Mac] Enter should trigger the buttons in the new avatar
bubble.

[commit-bot: I haz the power, 2014-10-17 22:21:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/640593006/1

[groby-ooo-7-16, 2014-10-17 22:21:31]

lgtm

[commit-bot: I haz the power, 2014-10-17 22:22:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-17 22:24:54]

Patchset 1 (id:??) landed as
https://crrev.com/4530a109e1867a9662ea92a3048e3db5e02dbd60
Cr-Commit-Position: refs/heads/master@{#300175}