Drop isindex from HTMLTagNames.

Source/build/scripts/make_element_factory.py

 #!/usr/bin/env python
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 60 matching lines @@
 
         interface_counts = defaultdict(int)
         tags = self._template_context['tags']
         for tag in tags:
             tag['has_js_interface'] = self._has_js_interface(tag)
             tag['js_interface'] = self._js_interface(tag)
             tag['interface'] = self._interface(tag)
             interface_counts[tag['interface']] += 1
 
         for tag in tags:
-            tag['multipleTagNames'] = interface_counts[tag['interface']] > 1
+            tag['multipleTagNames'] = (interface_counts[tag['interface']] > 1 or tag['interface'] == fallback_interface)
 
         self._template_context.update({
             'fallback_interface': fallback_interface,
             'fallback_js_interface': fallback_js_interface,
         })
 
     @template_expander.use_jinja('ElementFactory.h.tmpl', filters=filters)
     def generate_factory_header(self):
         return self._template_context
 
@@ skipping 26 matching lines @@
         if tag['JSInterfaceName']:
             return tag['JSInterfaceName']
         return self._interface(tag)
 
     def _has_js_interface(self, tag):
         return not tag['noConstructor'] and self._js_interface(tag) != ('%sElement' % self.namespace)
 
 
 if __name__ == "__main__":
     in_generator.Maker(MakeElementFactoryWriter).main(sys.argv)