Make tests/clipping/canvas-rounded-corners.sky actually run.

sky/engine/bindings/scripts/dart_interface.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 # coding=utf-8
 #
 # 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
@@ skipping 151 matching lines @@
                # Skip anonymous special operations (methods name empty).
                if (method.name and
                    # detect unnamed getters from v8_interface.
                    method.name != 'anonymousNamedGetter')]
     compute_method_overloads_context(methods)
     for method in methods:
         method['do_generate_method_configuration'] = (
             # For overloaded methods, only generate one accessor
             ('overload_index' not in method or method['overload_index'] == 1))
 
+    for method in methods:
+        assert 'overloads' not in method, 'Dart does not support overloads, %s in %s' % (method['name'], interface.name)
+
     generate_method_native_entries(interface, methods, 'Method')
 
     context.update({
         'has_method_configuration': any(method['do_generate_method_configuration'] for method in methods),
         'methods': methods,
     })
 
     context.update({
         'indexed_property_getter': indexed_property_getter(interface),
         'indexed_property_setter': indexed_property_setter(interface),
@@ skipping 550 matching lines @@
           ]
     props = [(p1 + "_" + p2, name, arity)
              for (p1, (p2, name, arity)) in itertools.product(pre, post)]
     for t in props:
         add(*t)
 
     for (p, name, arity) in props:
         if context[p]:
             if context[p].get('is_custom_property_query'):
                 add(p, '__propertyQuery__', 1)