Clean up the IDL compiler around [SetWrapperReferenceFrom/To]

Source/bindings/scripts/idl_definitions.py

 # 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
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 867 matching lines @@
             if child_class and child_class != 'Arguments':
                 raise ValueError('[CustomConstructor] only supports Arguments as child, but has child of class: %s' % child_class)
             custom_constructors.append(child)
         elif name == 'NamedConstructor':
             if child_class and child_class != 'Call':
                 raise ValueError('[NamedConstructor] only supports Call as child, but has child of class: %s' % child_class)
             extended_attributes[name] = child
         elif name == 'SetWrapperReferenceTo':
             if not child:
                 raise ValueError('[SetWrapperReferenceTo] requires a child, but has none.')
+            children = child.GetChildren()
+            if len(children) != 1:
+                raise ValueError('[SetWrapperReferenceTo] supports only one child.')
             if child_class != 'Arguments':
                 raise ValueError('[SetWrapperReferenceTo] only supports Arguments as child, but has child of class: %s' % child_class)
-            extended_attributes[name] = arguments_node_to_arguments(idl_name, child)
+            extended_attributes[name] = IdlArgument(idl_name, children[0])
         elif name == 'Exposed':
             if child_class and child_class != 'Arguments':
                 raise ValueError('[Exposed] only supports Arguments as child, but has child of class: %s' % child_class)
             exposures = []
             if child_class == 'Arguments':
                 exposures = [Exposure(exposed=str(arg.idl_type),
                                       runtime_enabled=arg.name)
                              for arg in arguments_node_to_arguments('*', child)]
             else:
                 value = extended_attribute_node.GetProperty('VALUE')
@@ skipping 180 matching lines @@
         self.visit_typed_object(argument)
 
     def visit_iterable(self, iterable):
         self.visit_typed_object(iterable)
 
     def visit_maplike(self, maplike):
         self.visit_typed_object(maplike)
 
     def visit_setlike(self, setlike):
         self.visit_typed_object(setlike)