Support bounded mixins in the VM (fix issue 14453).

tests/language/mixin_mixin_bound2_test.dart

+// Copyright (c) 2014, 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<U extends Set<V>, V> { }
+
+class M<U, V, T extends Map<U, V>> {
+  m() { return T; }
+}
+
+class A<U, V extends Set<U>> = Object with M<U, V, Map<U, V>> implements I<V>;
+
+class B<T extends List<num>> = Object with A<T, Set<T>> implements J<T>;
+
+class C<T extends num> = S<Set<T>, 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<Set<int>, int>);
+  Expect.isTrue(c is A<List<int>, Set<List<int>>>);
+  Expect.isTrue(c is M<List<int>, Set<List<int>>, Map<List<int>, Set<List<int>>>>);
+}