Add a basic demo mode browser test.

chrome/browser/chromeos/login/parallel_authenticator.cc

Index: chrome/browser/chromeos/login/parallel_authenticator.cc
diff --git a/chrome/browser/chromeos/login/parallel_authenticator.cc b/chrome/browser/chromeos/login/parallel_authenticator.cc
index 29ffe01df4da276ab7900e54bca1ab2e094bd509..e78004f808bf2f0458a9a60b3d20e23bd203ea49 100644
--- a/chrome/browser/chromeos/login/parallel_authenticator.cc
+++ b/chrome/browser/chromeos/login/parallel_authenticator.cc
@@ -346,11 +346,12 @@ void ParallelAuthenticator::LoginAsPublicAccount(const std::string& username) {
 }
 
 void ParallelAuthenticator::LoginAsKioskAccount(
-    const std::string& app_user_id, bool force_ephemeral) {
+    const std::string& app_user_id,
+    bool force_guest) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  std::string user_id =
-      force_ephemeral ? UserManager::kGuestUserName : app_user_id;
+  const std::string user_id =
+      force_guest ? UserManager::kGuestUserName : app_user_id;
   current_state_.reset(new AuthAttemptState(
       UserContext(user_id,
                   std::string(),  // password
@@ -361,7 +362,7 @@ void ParallelAuthenticator::LoginAsKioskAccount(
       false));
 
   remove_user_data_on_failure_ = true;
-  if (!force_ephemeral) {
+  if (!force_guest) {
     MountPublic(current_state_.get(),
           scoped_refptr<ParallelAuthenticator>(this),
           cryptohome::CREATE_IF_MISSING);