Mixin tests with libraries

tests/language/mixin_lib_extends_method_lib.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.
+
+library mixin_lib_extends_method_lib;
+
+class M1 {
+  bar() => "M1-bar";
+
+  clo(s) {
+    var l = s;
+    return (s) => "$l$s";
+  }
+}
+
+class M2 {
+  // Make sure mixed-in method has access to library-private names.
+  bar() => _M2_bar();
+  baz() => _M2_baz;
+  fez() => "M2-${_fez()}";
+  _fez() => "fez";
+}
+
+_M2_bar() {
+  return "M2-bar";
+}
+
+var _M2_baz = "M2-baz";