[cros] Fix tests: Reach the "Add user" screen before attempting to login

chrome/test/pyautolib/pyauto.py

Index: chrome/test/pyautolib/pyauto.py
diff --git a/chrome/test/pyautolib/pyauto.py b/chrome/test/pyautolib/pyauto.py
index dfe25d69bf43b129f724881405d67290df00a2aa..41e9924e8502b4097b4591ebb774be16cfaeccb8 100755
--- a/chrome/test/pyautolib/pyauto.py
+++ b/chrome/test/pyautolib/pyauto.py
@@ -4603,6 +4603,10 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     Raises:
       pyauto_errors.JSONInterfaceError if the automation call returns an error.
     """
+    # Go to the 'Add user' screen for login to work.
+    self.ExecuteJavascriptInOOBEWebUI(
+              'Oobe.showSigninUI();'
+              'window.domAutomationController.send("ok");')
     self._GetResultFromJSONRequest({'command': 'AddLoginEventObserver'},
                                    windex=None)
     cmd_dict = {