Add LoginState class to src/chromeos/login

ash/system/user/login_status.h

Index: ash/system/user/login_status.h
diff --git a/ash/system/user/login_status.h b/ash/system/user/login_status.h
index c1e54f8c73163948c9fd5ed67cedeef46fadc7f7..4a9d40fec91a05697644acb64433eb1b1d6bcd30 100644
--- a/ash/system/user/login_status.h
+++ b/ash/system/user/login_status.h
@@ -17,8 +17,6 @@ enum LoginStatus {
   LOGGED_IN_GUEST,            // A guest is logged in (i.e. incognito)
   LOGGED_IN_RETAIL_MODE,      // Is in retail mode.
   LOGGED_IN_PUBLIC,           // A public account is logged in.
-  LOGGED_IN_LOCALLY_MANAGED,  // A locally managed user is logged in.

[Nikita (slow), 2013/04/05 04:08:53]

Please leave LOGGED_IN_LOCALLY_MANAGED status as we most likely to configure
some UI elements based on that later.
If we end up not using it, I'll do a cleanup.

[stevenjb, 2013/04/05 18:17:15]

Ugh, another place where we were setting this in PowerButtonObserver, but not in
AshSystemTrayDelegate. Cleanup FTW. Done.

-  LOGGED_IN_KIOSK_APP,        // Is in kiosk app mode.

[bartfab (slow), 2013/04/05 13:16:33]

1/ Please leave the LOGGED_IN_KIOSK_APP status. This mode is still in flux,
which is why you do not see the status used anywhere yet.

2/ Nit: I presume that this constant means a kiosk app mode session is actually
running. A better comment would then be "Kiosk app session in progress."

3/ @xiyuan: I strongly object to yet another usage of "kiosk". It is way
overloaded already. Can we please rename this to something like
"LOGGED_IN_SINGLE_APP" for "single-app mode"?

[stevenjb, 2013/04/05 18:17:15]

I'm going to restore this to how it was, with any future renaming TBD by someone
who is familiar with it :)

   LOGGED_IN_NONE,             // Not logged in.
 };