bindings: [Replaceable] must not be specified with [PutForwards].

Source/bindings/scripts/v8_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 436 matching lines @@
 def access_control_list(interface, attribute):
     extended_attributes = attribute.extended_attributes
     access_control = []
     if 'DoNotCheckSecurity' in extended_attributes:
         do_not_check_security = extended_attributes['DoNotCheckSecurity']
         if do_not_check_security == 'Setter':
             access_control.append('v8::ALL_CAN_WRITE')
         else:
             access_control.append('v8::ALL_CAN_READ')
             if (not attribute.is_read_only or
+                'PutForwards' in extended_attributes or
                 'Replaceable' in extended_attributes):
                 access_control.append('v8::ALL_CAN_WRITE')
     if is_unforgeable(interface, attribute):
         access_control.append('v8::PROHIBITS_OVERWRITING')
     return access_control or ['v8::DEFAULT']
 
 
 # [NotEnumerable], [Unforgeable]
 def property_attributes(interface, attribute):
     extended_attributes = attribute.extended_attributes
@@ skipping 30 matching lines @@
     lambda self: strip_suffix(self.base_type, 'Constructor'))
 
 
 def is_constructor_attribute(attribute):
     # FIXME: replace this with [ConstructorAttribute] extended attribute
     return attribute.idl_type.name.endswith('Constructor')
 
 
 def constructor_getter_context(interface, attribute, context):
     context['needs_constructor_getter_callback'] = context['measure_as'] or context['deprecate_as']