IDL: Support nullable union types

Source/bindings/scripts/compute_interfaces_info_individual.py

 #!/usr/bin/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.
@@ skipping 115 matching lines @@
 def get_put_forward_interfaces_from_definition(definition):
     return sorted(set(attribute.idl_type.base_type
                       for attribute in definition.attributes
                       if 'PutForwards' in attribute.extended_attributes))
 
 
 def collect_union_types_from_definitions(definitions):
     """Traverse definitions and collect all union types."""
 
     def union_types_from(things):
-        return (thing.idl_type for thing in things
+        return (thing.idl_type.as_union_type for thing in things
                 if thing.idl_type.is_union_type)
 
     this_union_types = set()
     for interface in definitions.interfaces.itervalues():
         this_union_types.update(union_types_from(interface.attributes))
         for operation in interface.operations:
             this_union_types.update(union_types_from(operation.arguments))
             if operation.idl_type.is_union_type:
                 this_union_types.add(operation.idl_type)
         for constructor in interface.constructors:
@@ skipping 129 matching lines @@
 
     write_pickle_file(options.interfaces_info_file,
                       info_collector.get_info_as_dict(),
                       options.write_file_only_if_changed)
     write_pickle_file(options.component_info_file,
                       info_collector.get_component_info_as_dict(),
                       options.write_file_only_if_changed)
 
 if __name__ == '__main__':
     sys.exit(main())