Add support for Chrome policy type that references external data

grit/format/policy_templates/writers/reg_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 grit.format.policy_templates.writers import template_writer
 
 
 def GetWriter(config):
@@ skipping 34 matching lines @@
     list.sort() methods to sort policies.
     See TemplateWriter.SortPoliciesGroupsFirst for usage.
     '''
     is_list = policy['type'] == 'list'
     # Lists come after regular policies.
     return (is_list, policy['name'])
 
   def _WritePolicy(self, policy, key, list):
     example_value = policy['example_value']
 
-    if policy['type'] == 'list':
+    if policy['type'] == 'external':
+      # This type can only be set through cloud policy.
+      return
+    elif policy['type'] == 'list':
       self._StartBlock(key, policy['name'], list)
       i = 1
       for item in example_value:
         escaped_str = self._EscapeRegString(item)
         list.append('"%d"="%s"' % (i, escaped_str))
         i = i + 1
     else:
       self._StartBlock(key, None, list)
       if policy['type'] in ('string', 'dict'):
         escaped_str = self._EscapeRegString(str(example_value))
@@ skipping 30 matching lines @@
 
   def Init(self):
     self._mandatory = []
     self._recommended = []
     self._last_key = {}
 
   def GetTemplateText(self):
     prefix = ['Windows Registry Editor Version 5.00']
     all = prefix + self._mandatory + self._recommended
     return self.NEWLINE.join(all)