Fix focus visibility and style for GAIA Back and Close buttons

Fix focus visibility and style for GAIA Back and Close buttons

BUG=478429, 478545
The Back and Close buttons are now styled as per
https://code.google.com/p/chromium/issues/detail?id=478545#c9

There is no animated ripple effect, and they do not use polymer, but are
otherwise in line with the requests of this issue.  Fixes apply to both
regular login and Enterprise Enrollment flows.

Committed: https://crrev.com/b916ecb5d789e40c97c8b1ddaec9ea1ee029cad6
Cr-Commit-Position: refs/heads/master@{#328849}

[Greg Levin, 2015-05-06 00:23:57]

glevin@chromium.org changed reviewers:
+ nkostylev@chromium.org

[Greg Levin, 2015-05-06 00:23:58]

Please have a look

https://codereview.chromium.org/1121723004/diff/1/chrome/browser/resources/ch...
File
chrome/browser/resources/chromeos/login/oobe_screen_oauth_enrollment_webview.html
(right):

https://codereview.chromium.org/1121723004/diff/1/chrome/browser/resources/ch...
chrome/browser/resources/chromeos/login/oobe_screen_oauth_enrollment_webview.html:85:
i18n-values="aria-label:closeButton" tabindex="0"></button>
Moved down here to place buttons after other GAIA elements in TAB order (same as
in screen_gaia_signin.html).

https://codereview.chromium.org/1121723004/diff/1/chrome/browser/resources/ch...
File chrome/browser/resources/chromeos/login/screen_gaia_signin.css (right):

https://codereview.chromium.org/1121723004/diff/1/chrome/browser/resources/ch...
chrome/browser/resources/chromeos/login/screen_gaia_signin.css:94: }
This overrides (removes) the light blue halo which appeared around the perimeter
of the solid grey focus circle.

[Nikita (slow), 2015-05-07 12:30:16]

nkostylev@chromium.org changed reviewers:
+ dzhioev@chromium.org
- nkostylev@chromium.org

[Nikita (slow), 2015-05-07 12:30:17]

I'll let Pavel dzhioev@ review this CL since he's now in MTV timezone.

[dzhioev (left Google), 2015-05-07 20:51:29]

On 2015/05/07 12:30:17, Nikita wrote:
> I'll let Pavel dzhioev@ review this CL since he's now in MTV timezone.

LGTM

[Greg Levin, 2015-05-07 21:11:24]

The CQ bit was checked by glevin@chromium.org

[commit-bot: I haz the power, 2015-05-07 21:13:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1121723004/1

[commit-bot: I haz the power, 2015-05-07 22:00:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-07 22:02:43]

Patchset 1 (id:??) landed as
https://crrev.com/b916ecb5d789e40c97c8b1ddaec9ea1ee029cad6
Cr-Commit-Position: refs/heads/master@{#328849}