Allow substitution of messages as variables in other messages.

grit/format/policy_templates/template_formatter.py

Index: grit/format/policy_templates/template_formatter.py
diff --git a/grit/format/policy_templates/template_formatter.py b/grit/format/policy_templates/template_formatter.py
index 906f2e1c5856be0cc386b28161a921290a1c4940..1bd012939d558f9848ff2ca64d6f54d2b8c2551c 100644
--- a/grit/format/policy_templates/template_formatter.py
+++ b/grit/format/policy_templates/template_formatter.py
@@ -44,7 +44,7 @@ class TemplateFormatter(interface.ItemFormatter):
     # The module that contains the writer class:
     self._writer_module = sys.modules[writer_module_name]
 
-  def Format(self, item, lang='en', begin_item=True, output_dir='.'):
+  def Format(self, item, lang='en', output_dir='.'):
     '''Generates a template corresponding to an <output> node in the grd file.
 
     Args:
@@ -57,9 +57,6 @@ class TemplateFormatter(interface.ItemFormatter):
     Returns:
       The text of the template file.
     '''
-    if not begin_item:
-      return ''
-
     self._lang = lang
     self._config = writer_configuration.GetConfigurationForBuild(item.defines)
     self._policy_data = None