Add Lasse's test case from dartbug.com/6451.

tests/language/invocation_mirror2_test.dart

Index: tests/language/invocation_mirror2_test.dart
===================================================================
--- tests/language/invocation_mirror2_test.dart	(revision 0)
+++ tests/language/invocation_mirror2_test.dart	(revision 0)
@@ -0,0 +1,16 @@
+// Copyright (c) 2012, 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.
+
+class C {
+  var im;
+  noSuchMethod(im) => this.im = im;
+  flif() {}
+}
+
+main() {
+ var c = new C();
+ c.flif = 42;
+ Expect.equals('flif=', c.im.memberName);
+ Expect.equals(42, c.im.positionalArguments[0]);
+}