Add a basic demo mode browser test.

chrome/browser/chromeos/login/parallel_authenticator.h

Index: chrome/browser/chromeos/login/parallel_authenticator.h
diff --git a/chrome/browser/chromeos/login/parallel_authenticator.h b/chrome/browser/chromeos/login/parallel_authenticator.h
index 8ea765a59372a76e1ef6a656d20e3f4ffb95c599..8936d51112a02cfab0a1b046597e1546085e7f21 100644
--- a/chrome/browser/chromeos/login/parallel_authenticator.h
+++ b/chrome/browser/chromeos/login/parallel_authenticator.h
@@ -132,10 +132,13 @@ class ParallelAuthenticator : public Authenticator,
   virtual void LoginAsPublicAccount(const std::string& username) OVERRIDE;
 
   // Initiates login into the kiosk mode account identified by |app_user_id|.
-  // Mounts an public but non-ephemeral cryptohome and notifies consumer on the
-  // success/failure.
-  virtual void LoginAsKioskAccount(
-      const std::string& app_user_id, bool force_ephemeral) OVERRIDE;
+  // Mounts a public cryptohome and notifies the consumer on the
+  // success/failure. If |force_guest| is true, instead we mount a guest
+  // cryptohome (which is ephemeral), otherwise the mount is non-ephemeral.
+  // If the |DeviceEphemeralUsersEnabled| policy is enabled, even if
+  // force_guest is false, a (non-guest) ephemeral cryptohome will be mounted.

[bartfab (slow), 2014/03/25 12:52:54]

This looks correct but a bit convoluted, in that it states that the mount
normally is non-ephemeral but then immediately contradicts that statement under
certain conditions. How about something along the lines of (with |force_guest|
replaced by |use_guest_mount|, as suggested elsewhere):

Mounts an ephemeral guest cryptohome if |use_guest_mount| is |true|. Otherwise,
mounts a public cryptohome, which will be ephemeral if the
|DeviceEphemeralUsersEnabled| policy is enabled and non-ephemeral otherwise.

[rkc, 2014/03/26 21:30:40]

Done.

+  virtual void LoginAsKioskAccount(const std::string& app_user_id,
+                                   bool force_guest) OVERRIDE;
 
   // These methods must be called on the UI thread, as they make DBus calls
   // and also call back to the login UI.