Add session object so that we have one class that control logged in session

client/site_tests/desktopui_ChromeFirstRender/desktopui_ChromeFirstRender.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, re
-from autotest_lib.client.bin import test
+import logging, re, time
+from autotest_lib.client.bin import site_ui_test
 from autotest_lib.client.common_lib import error
 
-class desktopui_ChromeFirstRender(test.test):
+class desktopui_ChromeFirstRender(site_ui_test.UITest):
     version = 1
 
+
     def __parse_uptime(self, target_file):
         data = file(target_file).read()
         time = re.split(r' +', data.strip())[0]
         return float(time)
-
+        
 
     def run_once(self):
-        try:
+        try:            
+            time.sleep(10) # Wait for chrome to render.
             start_time = self.__parse_uptime('/tmp/uptime-login-successful')
             end_time = self.__parse_uptime('/tmp/uptime-chrome-first-render')
             self.write_perf_keyval({'seconds_chrome_first_tab':
-                                      end_time - start_time})
+                                      end_time - start_time})            
         except IOError, e:
             logging.debug(e)
             raise error.TestFail('Login information missing')