Fix SHIFT+TAB order on GAIA login screens

Fix SHIFT+TAB order on GAIA login screens

BUG=488664
TEST=SHIFT+TAB repeatedly through login screen.

When focus is on the system tray, SHIFT+TAB should move focus onto the
[...] button, or whatever is the previous button on the shelf.
Previously, TAB and SHIFT+TAB would both move focus onto "Enter your
email" (or somewhere else in the GAIA elements).

Committed: https://crrev.com/eb2fad4839df15e0fee76f6a4f7beebf0244e167
Cr-Commit-Position: refs/heads/master@{#333803}

[Greg Levin, 2015-06-10 17:31:38]

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

[Greg Levin, 2015-06-10 17:31:39]

Please take a quick look... I'd like to try to squeeze this into 44 if possible.

Context of fix:
https://codereview.chromium.org/862543002/diff/20001/chrome/browser/resources...
was added to fix Issue 449495 in the browser.  On the new login page, however,
after focus was correctly placed on the [...] button, this code would then grab
focus and put it back on GAIA.  This fix prevents that, and leaves focus where
it should be.

[xiyuan, 2015-06-10 17:43:04]

https://codereview.chromium.org/1173083003/diff/1/chrome/browser/resources/ga...
File chrome/browser/resources/gaia_auth_host/authenticator.js (right):

https://codereview.chromium.org/1173083003/diff/1/chrome/browser/resources/ga...
chrome/browser/resources/gaia_auth_host/authenticator.js:325: if
(!this.isNewGaiaFlowChromeOS)
It is probably more correct to check (authMode == AuthMode.DESKTOP). 
How about remember authMode in Authenticator.prototype.load and test it here?

The worry is that we might switch to new gaia flow in ChromeOS mirror later and
would run it in a tab as well. And isNewGaiaFlowChromeOS might not tell the
difference.

[Greg Levin, 2015-06-10 20:01:25]

How does this look?

https://codereview.chromium.org/1173083003/diff/1/chrome/browser/resources/ga...
File chrome/browser/resources/gaia_auth_host/authenticator.js (right):

https://codereview.chromium.org/1173083003/diff/1/chrome/browser/resources/ga...
chrome/browser/resources/gaia_auth_host/authenticator.js:325: if
(!this.isNewGaiaFlowChromeOS)
On 2015/06/10 17:43:03, xiyuan wrote:
> It is probably more correct to check (authMode == AuthMode.DESKTOP). 
> How about remember authMode in Authenticator.prototype.load and test it here?
> 
> The worry is that we might switch to new gaia flow in ChromeOS mirror later
and
> would run it in a tab as well. And isNewGaiaFlowChromeOS might not tell the
> difference.

Done.

[xiyuan, 2015-06-10 20:15:55]

lgtm

Awesome. Thanks.

[Greg Levin, 2015-06-10 20:35:04]

The CQ bit was checked by glevin@chromium.org

[commit-bot: I haz the power, 2015-06-10 20:36:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1173083003/20001

[commit-bot: I haz the power, 2015-06-10 21:26:10]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-10 21:27:58]

Patchset 2 (id:??) landed as
https://crrev.com/eb2fad4839df15e0fee76f6a4f7beebf0244e167
Cr-Commit-Position: refs/heads/master@{#333803}