Throw when reflecting on elements not covered by a `MirrorsUsed` annotation.

tests/compiler/dart2js_extra/mirror_invalid_invoke2_test.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.
+
+// Test that we cannot reflect on elements not covered by the `MirrorsUsed`
+// annotation.
+
+library test;
+
+@MirrorsUsed(targets: 'C.foo')
+import 'dart:mirrors';
+
+import 'package:expect/expect.dart';
+
+import '../../language/compiler_annotations.dart';
+
+class C {
+  foo() => 1;
+
+  @DontInline
+  // Use a closure to prevent inlining until the annotation is implemented.
+  bar() => () => 2;
+}
+
+main() {
+  var c = new C();
+  c.bar();  // Call bar, so it is included in the program.
+
+  var mirror = reflect(c);
+  Expect.equals(1, mirror.invoke(const Symbol('foo'), []).reflectee);
+  Expect.throws(() => mirror.invoke(const Symbol('bar'),  []),
+                (e) => e is UnsupportedError);
+}