test: Clean up site_login.py a bit.

client/site_tests/desktopui_ScreenSaverUnlock/desktopui_ScreenSaverUnlock.py

 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging, os, time, utils
-from autotest_lib.client.bin import site_login, test
+from autotest_lib.client.bin import site_login, site_ui_test, test
 from autotest_lib.client.common_lib import error
 from autotest_lib.client.bin import chromeos_constants
 
-class desktopui_ScreenSaverUnlock(test.test):
+class desktopui_ScreenSaverUnlock(site_ui_test.UITest):
     version = 1
 
     def system_as(self, cmd, user='chronos'):
         utils.system('su %s -c \'%s\'' % (user, cmd))
 
-    def setup(self):
-        site_login.setup_autox(self)
-
     def run_once(self):
-        if site_login.logged_in():
-            if not site_login.attempt_logout():
-                raise error.TestFail('Could not terminate existing session')
-
-        if not site_login.attempt_login(self, 'autox_script.json'):
-            raise error.TestFail('Could not login')
-
-        # first sleep to let the login finish and start xscreensaver
-        time.sleep(10)
+        site_login.wait_for_screensaver()
         self.system_as('DISPLAY=:0.0 xscreensaver-command -lock')
 
         # some sleep to let the screen lock
+        # TODO: Sleeping is unreliable and slow.  Do something better to
+        # wait for the screen to be locked.
         time.sleep(5)
         self.system_as('DISPLAY=:0.0 xscreensaver-command -time | ' +
                        'grep -q locked')
 
         time.sleep(10)
-        if not site_login.attempt_login(self, 'autox_unlock.json'):
-            raise error.TestFail('Could not unlock screensaver')
+        site_login.attempt_login(self, 'autox_unlock.json')
 
         # wait for screen to unlock
         time.sleep(5)
         self.system_as('DISPLAY=:0.0 xscreensaver-command -time | ' +
                        'grep -q non-blanked')