IDL: Support [Unforgeable] on interface definitions

Source/bindings/scripts/v8_utilities.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 383 matching lines @@
     Given extended attribute RuntimeEnabled=FeatureName, return:
         RuntimeEnabledFeatures::{featureName}Enabled
     """
     extended_attributes = definition_or_member.extended_attributes
     if 'RuntimeEnabled' not in extended_attributes:
         return None
     feature_name = extended_attributes['RuntimeEnabled']
     return 'RuntimeEnabledFeatures::%sEnabled' % uncapitalize(feature_name)
 
 
+# [Unforgeable]
+def is_unforgeable(interface, member):
+    return ('Unforgeable' in interface.extended_attributes or
+            'Unforgeable' in member.extended_attributes)
+
+
 ################################################################################
 # Indexed properties
 # http://heycam.github.io/webidl/#idl-indexed-properties
 ################################################################################
 
 def indexed_property_getter(interface):
     try:
         # Find indexed property getter, if present; has form:
         # getter TYPE [OPTIONAL_IDENTIFIER](unsigned long ARG1)
         return next(
@@ skipping 82 matching lines @@
     except StopIteration:
         return None
 
 
 IdlInterface.indexed_property_getter = property(indexed_property_getter)
 IdlInterface.indexed_property_setter = property(indexed_property_setter)
 IdlInterface.indexed_property_deleter = property(indexed_property_deleter)
 IdlInterface.named_property_getter = property(named_property_getter)
 IdlInterface.named_property_setter = property(named_property_setter)
 IdlInterface.named_property_deleter = property(named_property_deleter)