[cros] Fake a stub user login when no --login-manager and --login-user are given.

chrome/browser/chromeos/login/user_manager_impl.h

Index: chrome/browser/chromeos/login/user_manager_impl.h
diff --git a/chrome/browser/chromeos/login/user_manager_impl.h b/chrome/browser/chromeos/login/user_manager_impl.h
index 9f90110759af7602d5079856a38086bbd7c61ce4..0bb7b07fc82cf9a17af086c279b419a26d480c52 100644
--- a/chrome/browser/chromeos/login/user_manager_impl.h
+++ b/chrome/browser/chromeos/login/user_manager_impl.h
@@ -154,9 +154,6 @@ class UserManagerImpl : public UserManager,
   // list. Returns |NULL| otherwise.
   const User* FindUserInList(const std::string& email) const;
 
-  // Makes stub user the current logged-in user (for test paths).
-  void StubUserLoggedIn();
-
   // Notifies on new user session.
   void NotifyOnLogin();
 
@@ -316,8 +313,7 @@ class UserManagerImpl : public UserManager,
 
   // The logged-in user. NULL until a user has logged in, then points to one
   // of the User instances in |users_|, the |guest_user_| instance or an
-  // ephemeral user instance. In test paths without login points to the
-  // |stub_user_| instance.
+  // ephemeral user instance.
   User* logged_in_user_;
 
   // True if SessionStarted() has been called.