bindings: Throw TypeError when required dictionary member is undefined

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 204 matching lines @@
         for member in self.members:
             member.accept(visitor)
 
 
 class IdlDictionaryMember(TypedObject):
     def __init__(self, idl_name, node):
         self.default_value = None
         self.extended_attributes = {}
         self.idl_type = None
         self.idl_name = idl_name
+        self.is_required = bool(node.GetProperty('REQUIRED'))
         self.name = node.GetName()
         for child in node.GetChildren():
             child_class = child.GetClass()
             if child_class == 'Type':
                 self.idl_type = type_node_to_type(child)
             elif child_class == 'Default':
                 self.default_value = default_node_to_idl_literal(child)
             elif child_class == 'ExtAttributes':
                 self.extended_attributes = (
                     ext_attributes_node_to_extended_attributes(idl_name, child))
@@ skipping 826 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)