Allow getField of methods.

tests/compiler/dart2js_extra/mirrors_used_closure_test.dart

+// Copyright (c) 2014, 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 MirrorsTest;
+
+import 'package:expect/expect.dart';
+
+@MirrorsUsed(targets: const ['A.foo', 'B.bar'])
+import 'dart:mirrors';
+
+class A {
+  foo() => 42;
+  bar() => 499;
+}
+
+class B {
+  bar() => 33;
+}
+
+// Uses DateTime.now to make it impossible to predict.
+// Uses recursive call to make it harder to inline.
+confuse(x) {
+  if (new DateTime.now().millisecondsSinceEpoch == 42) return confuse(x + 1);
+  return x;
+}
+
+main() {
+  var f = [new A(), new B()][confuse(0)].bar;
+  Expect.throws(() => reflect(f).invoke(#call, [], {}),
+                (e) => e is UnsupportedError);
+}