Make nullable DOMString always treat undefined as null

third_party/WebKit/Source/bindings/scripts/v8_types.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 126 matching lines @@
             type of a method.
         used_as_variadic_argument:
             bool, True if the C++ type is used as a variadic argument of a method.
         used_in_cpp_sequence:
             bool, True if the C++ type is used as an element of a container.
             Containers can be an array, a sequence or a dictionary.
     """
     def string_mode():
         if extended_attributes.get('TreatNullAs') == 'EmptyString':
             return 'TreatNullAsEmptyString'
-        if idl_type.is_nullable or extended_attributes.get('TreatNullAs') == 'NullString':
+        if extended_attributes.get('TreatNullAs') == 'NullString':
             if extended_attributes.get('TreatUndefinedAs') == 'NullString':
                 return 'TreatNullAndUndefinedAsNullString'
             return 'TreatNullAsNullString'
+        if idl_type.is_nullable:
+            return 'TreatNullAndUndefinedAsNullString'
         return ''
 
     extended_attributes = extended_attributes or {}
     idl_type = idl_type.preprocessed_type
 
     # Array or sequence types
     if used_as_variadic_argument:
         native_array_element_type = idl_type
     else:
         native_array_element_type = idl_type.native_array_element_type
@@ skipping 845 matching lines @@
     number_of_nullable_member_types_union)
 
 
 def includes_nullable_type_union(idl_type):
     # http://heycam.github.io/webidl/#dfn-includes-a-nullable-type
     return idl_type.number_of_nullable_member_types == 1
 
 IdlTypeBase.includes_nullable_type = False
 IdlNullableType.includes_nullable_type = True
 IdlUnionType.includes_nullable_type = property(includes_nullable_type_union)