More mixin super tests.

tests/language/mixin_super_2_test.dart

+// Copyright (c) 2015, 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.
+// SharedOptions=--supermixin
+
+import "package:expect/expect.dart";
+
+class B {
+  // 'super' resolves to Object, and in some tests, multiple points in the
+  // inheritance chain.
+  toString() => 'B(' + super.toString() + ')';
+}
+
+class R {
+  toString() => 'R[' + super.toString() + ']';
+}
+
+class D extends R with B {
+  toString() => 'D<' + super.toString() + '>';
+}
+
+class E extends D with B {
+  toString() => 'E{' + super.toString() + '}';
+}
+
+class F = R with B, B;
+
+class G extends F with B {
+  toString() => 'G{' + super.toString() + '}';
+}
+
+main(){
+  check(object, String expected) {
+    Expect.equals(expected, object.toString());
+  }
+
+  check(new B(), "B(Instance of 'B')");
+  check(new R(), "R[Instance of 'R']");
+  check(new D(), "D<B(R[Instance of 'D'])>");
+  check(new E(), "E{B(D<B(R[Instance of 'E'])>)}");
+  check(new F(), "B(B(R[Instance of 'F']))");
+  check(new G(), "G{B(B(B(R[Instance of 'G'])))}");
+}