Add optional mandatory policy setting for template generation

grit/format/policy_templates/writers/json_writer.py

Index: grit/format/policy_templates/writers/json_writer.py
===================================================================
--- grit/format/policy_templates/writers/json_writer.py	(revision 175)
+++ grit/format/policy_templates/writers/json_writer.py	(working copy)
@@ -49,6 +49,13 @@
     if not self._first_written:
       self._out[-2] += ','
 
+    if not self.CanBeMandatory(policy) and self.CanBeRecommended(policy):
+      line = '  // Note: this policy is supported only in recommended mode.'
+      self._out.append(line)
+      line = '  // The JSON file should be placed in %srecommended.' % \
+             self.config['linux_policy_path']
+      self._out.append(line)
+
     line = '  // %s' % policy['caption']
     self._out.append(line)
     self._out.append(HEADER_DELIMETER)