kiosk: Show enrollment screen first if needed.

kiosk: Show enrollment screen first if needed.

- Show enrollment screen by default after OOBE if the device is set
  to auto enrollment and is not yet enrolled;
- Update screen loading code to defer Initialize() call for async
  loaded screen until the assets are loaded;

BUG=322666
TEST=LoginUITest.ShowEnrollmentFirst

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=238262

[xiyuan, 2013-12-02 19:07:31]

ping?

[zel, 2013-12-02 19:12:33]

lgtm

[commit-bot: I haz the power, 2013-12-02 22:26:45]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/xiyuan@chromium.org/83293004/20001

[commit-bot: I haz the power, 2013-12-02 22:43:57]

Retried try job too often on chromium_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=chromium_p...

[commit-bot: I haz the power, 2013-12-02 22:48:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/xiyuan@chromium.org/83293004/210001

[commit-bot: I haz the power, 2013-12-03 01:25:58]

Change committed as 238262