IDL: Support optional argument default value syntax

Source/bindings/scripts/v8_methods.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 163 matching lines @@
     extended_attributes = argument.extended_attributes
     idl_type = argument.idl_type
     this_cpp_value = cpp_value(interface, method, index)
     is_variadic_wrapper_type = argument.is_variadic and idl_type.is_wrapper_type
 
     return {
         'cpp_type': idl_type.cpp_type_args(extended_attributes=extended_attributes,
                                            used_as_argument=True,
                                            used_as_variadic_argument=argument.is_variadic),
         'cpp_value': this_cpp_value,
+        # FIXME: check that the default value's type is compatible with the argument's
+        'default_value': str(argument.default_value) if argument.default_value else None,
         'enum_validation_expression': idl_type.enum_validation_expression,
-        'has_default': 'Default' in extended_attributes,
+        # FIXME: remove once [Default] removed and just use argument.default_value
+        'has_default': 'Default' in extended_attributes or argument.default_value,
         'has_event_listener_argument': any(
             argument_so_far for argument_so_far in method.arguments[:index]
             if argument_so_far.idl_type.name == 'EventListener'),
         'has_type_checking_interface':
             (has_extended_attribute_value(interface, 'TypeChecking', 'Interface') or
              has_extended_attribute_value(method, 'TypeChecking', 'Interface')) and
             idl_type.is_wrapper_type,
         'has_type_checking_unrestricted':
             (has_extended_attribute_value(interface, 'TypeChecking', 'Unrestricted') or
              has_extended_attribute_value(method, 'TypeChecking', 'Unrestricted')) and
@@ skipping 95 matching lines @@
 
     return '%s(%s)' % (macro, ', '.join(macro_args))
 
 
 def v8_value_to_local_cpp_value(argument, index):
     extended_attributes = argument.extended_attributes
     idl_type = argument.idl_type
     name = argument.name
     if argument.is_variadic:
         return v8_value_to_local_cpp_variadic_value(argument, index)
-    # [Default=NullString]
+    # FIXME: This special way of handling string arguments with null defaults
+    # can go away once we fully support default values.
     if (argument.is_optional and idl_type.name in ('String', 'ByteString') and
-        extended_attributes.get('Default') == 'NullString'):
+        argument.default_value and argument.default_value.is_null):
         v8_value = 'argumentOrNull(info, %s)' % index
     else:
         v8_value = 'info[%s]' % index
     return idl_type.v8_value_to_local_cpp_value(extended_attributes, v8_value,
                                                 name, index=index, declare_variable=False)
 
 
 ################################################################################
 # Auxiliary functions
 ################################################################################
@@ skipping 12 matching lines @@
 
 
 def union_arguments(idl_type):
     """Return list of ['result0Enabled', 'result0', 'result1Enabled', ...] for union types, for use in setting return value"""
     return [arg
             for i in range(len(idl_type.member_types))
             for arg in ['result%sEnabled' % i, 'result%s' % i]]
 
 IdlType.union_arguments = property(lambda self: None)
 IdlUnionType.union_arguments = property(union_arguments)