switch to autox.py and robustify login/logout code

client/common_lib/site_ui.py

Index: client/common_lib/site_ui.py
diff --git a/client/common_lib/site_ui.py b/client/common_lib/site_ui.py
index ffc515e5ec977032d28e89d424c04aa61749cb24..bdd0b3531293d8d59e055c68390f376cd4cb8f07 100644
--- a/client/common_lib/site_ui.py
+++ b/client/common_lib/site_ui.py
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import logging, shutil
+import logging, os, shutil
 from autotest_lib.client.common_lib import site_httpd, utils
 
 
@@ -44,6 +44,16 @@ def xsystem_as(cmd, user='chronos', timeout=None, ignore_status=False):
                         ignore_status=ignore_status)
 
 
+def get_autox():
+    """Return a new autox instance."""
+    # we're running as root, but need to connect to chronos' X session
+    os.environ.setdefault('XAUTHORITY', '/home/chronos/.Xauthority')
+    os.environ.setdefault('DISPLAY', ':0.0')
+
+    import autox
+    return autox.AutoX()
+
+
 class ChromeSession(object):
     """
     A class to start and close Chrome sessions.