Implement updated method overriding rules in the vm.

tests/language/class_override_negative_test.dart

Index: tests/language/class_override_negative_test.dart
===================================================================
--- tests/language/class_override_negative_test.dart	(revision 25979)
+++ tests/language/class_override_negative_test.dart	(working copy)
@@ -1,20 +0,0 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// 8.1 Methods: It is a compile-time error if a method m1 overrides
-// a method m2 and has a different number of required parameters.
-
-class A {
-  foo() {}
-}
-
-class B extends A {
-  foo(a) { }
-}
-
-main() {
-  B instance = new B();
-  instance.foo(1);
-  print("Success");
-}