Add support for Chrome policy type that references external data

grit/format/policy_templates/writers/admx_writer.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.
 
 from xml.dom import minidom
 from grit.format.policy_templates.writers import xml_formatted_writer
 
 
 def GetWriter(config):
@@ skipping 235 matching lines @@
       raise Exception('There is supposed to be only one "elements" node but'
                       ' there are %s.' % str(len(elements_list)))
 
   def _WritePolicy(self, policy, name, key, parent):
     '''Generates AMDX elements for a Policy. There are four different policy
     types: Main-Policy, String-Policy, Enum-Policy and List-Policy.
     '''
     policies_elem = self._active_policies_elem
     policy_type = policy['type']
     policy_name = policy['name']
+    if policy_type == 'external':
+      # This type can only be set through cloud policy.
+      return
 
     attributes = {
       'name': name,
       'class': self.config['win_group_policy_class'],
       'displayName': self._AdmlString(policy_name),
       'explainText': self._AdmlStringExplain(policy_name),
       'presentation': self._AdmlPresentation(policy_name),
       'key': key,
     }
     # Store the current "policy" AMDX element in self for later use by the
@@ skipping 97 matching lines @@
     self._AddCategories(self.config['win_recommended_category_path'])
     self._active_policies_elem = self.AddElement(policy_definitions_elem,
                                                  'policies')
     self._active_mandatory_policy_group_name = \
         self.config['win_mandatory_category_path'][-1]
     self._active_recommended_policy_group_name = \
         self.config['win_recommended_category_path'][-1]
 
   def GetTemplateText(self):
     return self.ToPrettyXml(self._doc)