Make it possible to inherit from any constructable host object

sky/engine/bindings/scripts/dart_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 88 matching lines @@
     })
     return context
 
 def argument_context(interface, method, argument, index):
     context = v8_methods.argument_context(interface, method, argument, index)
 
     extended_attributes = argument.extended_attributes
     idl_type = argument.idl_type
     this_cpp_value = cpp_value(interface, method, index)
     auto_scope = not 'DartNoAutoScope' in extended_attributes
-    arg_index = index + 1 if not (method.is_static or method.is_constructor) else index
+    arg_index = index + 1 if not method.is_static else index
     preprocessed_type = str(idl_type.preprocessed_type)
     local_cpp_type = idl_type.cpp_type_args(argument.extended_attributes, raw_type=True)
     default_value = argument.default_cpp_value
     if context['has_default']:
         default_value = (argument.default_cpp_value or
             dart_types.default_cpp_value_for_cpp_type(idl_type))
     dart_type = dart_types.idl_type_to_dart_type(idl_type)
     dart_default_value = dart_types.dart_default_value(dart_type, argument)
     context.update({
         'cpp_type': idl_type.cpp_type_args(extended_attributes=extended_attributes,
@@ skipping 117 matching lines @@
     # removeEventListener methods that should be added in somewhere.
     # There is also some logic in systemnative.py to force a null check
     # for the useCapture argument of those same methods that we may need to
     # pull over.
     null_check = ((argument.is_optional and idl_type.is_callback_interface) or
                   (argument.default_value and argument.default_value.is_null))
 
     return idl_type.dart_value_to_local_cpp_value(
         extended_attributes, name, null_check, has_type_checking_interface,
         index=index, auto_scope=auto_scope)