Import rasta tests.

pkg/fasta/test/rasta/super_mixin.dart

+// Copyright (c) 2016, 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.md file.
+
+import "mixin_library.dart" show Mixin;
+
+class Super<S> {
+  foo() => 40;
+  f() => 3;
+}
+
+class C<V> extends Super<V> with Mixin<V> {
+}
+
+class D extends Super with Mixin {
+}
+
+class C2<V> = Super<V> with Mixin<V>;
+
+class D2 = Super with Mixin;
+
+main() {
+  print(new C().foo());
+  print(new C2().foo());
+}