Bug 1133468 - Use wait_for_condition rather than immediately checking for a url update in marionette's modal handling code.;r=automatedtester

testing/marionette/client/marionette/tests/unit/test_modal_dialogs.py

@@ -152,7 +152,7 @@ class TestTabModals(MarionetteTestCase):
         alert = self.marionette.switch_to_alert()
         self.assertTrue(alert.text.startswith("This page is asking you to confirm"))
         alert.accept()
-        self.assertEqual(self.marionette.get_url(), "about:blank")
+        self.wait_for_condition(lambda mn: mn.get_url() == "about:blank")
 
     @skip_if_e10s
     def test_unrelated_command_when_alert_present(self):