Add null-correctness checking to [StrictTypeChecking] methods

Source/bindings/scripts/unstable/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 152 matching lines @@
         idl_type == 'EventHandler' or
         'CachedAttribute' in extended_attributes or
         contents['is_getter_raises_exception']):
         contents['cpp_value_original'] = cpp_value
         cpp_value = 'jsValue'
 
     if contents['is_keep_alive_for_gc']:
         v8_set_return_value_statement = 'v8SetReturnValue(info, wrapper)'
         includes.add('bindings/v8/V8HiddenPropertyName.h')
     else:
-        v8_set_return_value_statement = v8_types.v8_set_return_value(idl_type, cpp_value, extended_attributes=extended_attributes, script_wrappable='imp')
+        if attribute.is_nullable and v8_types.is_interface_type(idl_type):
+            set_cpp_value = 'jsValue.release()'
+        else:
+            set_cpp_value = cpp_value
+        v8_set_return_value_statement = v8_types.v8_set_return_value(idl_type, set_cpp_value, extended_attributes=extended_attributes, script_wrappable='imp')
 
     contents.update({
         'cpp_value': cpp_value,
         'v8_set_return_value': v8_set_return_value_statement,
     })
 
 
 def getter_expression(interface, attribute, contents):
     arguments = []
     this_getter_base_name = getter_base_name(attribute, arguments)
@@ skipping 160 matching lines @@
         property_attributes_list.append('v8::DontDelete')
     return property_attributes_list or ['v8::None']
 
 
 ################################################################################
 # Constructors
 ################################################################################
 
 def is_constructor_attribute(attribute):
     return attribute.idl_type.endswith('Constructor')