Disable modifying extensions when in managed mode.

chrome/test/functional/policy_prefs_ui.py

Index: chrome/test/functional/policy_prefs_ui.py
===================================================================
--- chrome/test/functional/policy_prefs_ui.py	(revision 142678)
+++ chrome/test/functional/policy_prefs_ui.py	(working copy)
@@ -50,11 +50,10 @@
       self.LoginWithTestAccount()
 
   def IsAnyBannerVisible(self):
-    """Returns true if any managed prefs banner is visible in the current page.
-    """
+    """Returns true if any banner (e.g. for managed prefs) is visible."""
     ret = self.ExecuteJavascript("""
         var visible = false;
-        var banners = document.querySelectorAll('.managed-prefs-banner');
+        var banners = document.querySelectorAll('.page-banner');
         for (var i=0; i<banners.length; i++) {
           if (banners[i].parentElement.id == 'templates')
             continue;