Disable modifying extensions when in managed mode.

chrome/test/functional/policy_prefs_ui.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # If this test is failing, please check these steps.
 #
 # - You introduced a new policy:
 #   Cool! Edit |policies| in policy_test_cases.py and add an entry for it.
 #   See the comment above it for the format.
@@ skipping 32 matching lines @@
     settings_pages += [
         'chrome://settings-frame/accounts',
     ]
 
   def setUp(self):
     policy_base.PolicyTestBase.setUp(self)
     if self.IsChromeOS():
       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;
 
           if (window.getComputedStyle(banners[i]).display != 'none')
             visible = true;
         }
         domAutomationController.send(visible.toString());
     """)
     return ret == 'true'
@@ skipping 105 matching lines @@
 
     self.SetUserPolicy(policy_dict)
     self.assertTrue(self.IsAnyBannerVisible())
 
     self.SetUserPolicy({})
     self.assertFalse(self.IsAnyBannerVisible())
 
 
 if __name__ == '__main__':
   pyauto_functional.Main()