Add mixin language tests.

tests/language/mixin_mixin5_test.dart

+// Copyright (c) 2013, 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.
+
+import "package:expect/expect.dart";
+
+class I<T> { }
+
+class J<T> { }
+
+class K<T> { }
+
+class S<T> { }
+
+class M<T> {
+  m() { return T; }
+}
+
+typedef A<U, V> = Object with M<Map<U, V>> implements I<V>;
+
+typedef B<T> = Object with A<T, Set<T>> implements J<T>;
+
+typedef C<T> = S<List<T>> with B<List<T>> implements K<T>;
+
+main() {
+  var c = new C<int>();
+  Expect.equals("Map<List<int>, Set<List<int>>>", c.m().toString());
+  Expect.isTrue(c is K<int>);
+  Expect.isTrue(c is J<List<int>>);
+  Expect.isTrue(c is I<Set<List<int>>>);
+  Expect.isTrue(c is S<List<int>>);
+  Expect.isTrue(c is A<List<int>, Set<List<int>>>);
+  Expect.isTrue(c is M<Map<List<int>, Set<List<int>>>>);
+}