Bindings generation emits (more) correct null checking

Source/bindings/dart/scripts/dart_attributes.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 287 matching lines @@
         try:
             return next(attribute
                         for attribute in target_interface.attributes
                         if attribute.name == target_attribute_name)
         except StopIteration:
             raise Exception('[PutForward] target not found:\n'
                             'Attribute "%s" is not present in interface "%s"' %
                             (target_attribute_name, target_interface_name))
 
     extended_attributes = attribute.extended_attributes
+    interface_extended_attributes = interface.extended_attributes
 
     if 'PutForwards' in extended_attributes:
         # Use target attribute in place of original attribute
         attribute = target_attribute()
         this_cpp_type = 'DartStringAdapter'
     else:
         this_cpp_type = contents['cpp_type']
 
     idl_type = attribute.idl_type
 
     # TODO(terry): Should be able to eliminate suppress_setter as we move from
     #              IGNORE_MEMBERS to DartSuppress in the IDL.
     suppress = (suppress_setter(interface.name, attribute.name) or
                 DartUtilities.has_extended_attribute_value(attribute, 'DartSuppress', 'Setter'))
     contents.update({
         'is_setter_suppressed':  suppress,
         'setter_lvalue': dart_types.check_reserved_name(attribute.name),
         'cpp_type': this_cpp_type,
         'local_cpp_type': idl_type.cpp_type_args(attribute.extended_attributes, used_as_argument=True),
         'cpp_setter': setter_expression(interface, attribute, contents),
         'dart_value_to_local_cpp_value':
             attribute.idl_type.dart_value_to_local_cpp_value(
-                extended_attributes, attribute.name, False, 1,
+                interface_extended_attributes, extended_attributes, attribute.name, False, 1,
                 contents['is_auto_scope']),
     })
 
 
 def setter_expression(interface, attribute, contents):
     extended_attributes = attribute.extended_attributes
     arguments = DartUtilities.call_with_arguments(attribute, extended_attributes.get('SetterCallWith'))
 
     this_setter_base_name = setter_base_name(interface, attribute, arguments)
     setter_name = DartUtilities.scoped_name(interface, attribute, this_setter_base_name)
@@ skipping 108 matching lines @@
     lambda self: DartUtilities.strip_suffix(self.base_type, 'Constructor'))
 
 
 def is_constructor_attribute(attribute):
     # FIXME: replace this with [ConstructorAttribute] extended attribute
     return attribute.idl_type.base_type.endswith('Constructor')
 
 
 def generate_constructor_getter(interface, attribute, contents):
     contents['needs_constructor_getter_callback'] = contents['measure_as'] or contents['deprecate_as']