Raise an exception instead of crashing when attempting to pass a MirrorReference between isolates.

tests/isolate/illegal_msg_function_test.dart

Index: tests/isolate/illegal_msg_function_test.dart
diff --git a/tests/isolate/illegal_msg_test.dart b/tests/isolate/illegal_msg_function_test.dart
similarity index 87%
copy from tests/isolate/illegal_msg_test.dart
copy to tests/isolate/illegal_msg_function_test.dart
index 422ae39a55d48705ccbd60a907810e77363a62ab..f967afd9d50d9c6580254bd73c72a92126aa0f3b 100644
--- a/tests/isolate/illegal_msg_test.dart
+++ b/tests/isolate/illegal_msg_function_test.dart
@@ -2,9 +2,11 @@
 // 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 illegal_msg_tests;
+library illegal_msg_function_test;
+
 import "package:expect/expect.dart";
-import 'dart:isolate';
+import "dart:isolate";
+import "dart:async" show Future;
 import "package:async_helper/async_helper.dart";
 
 funcFoo(x) => x + 2;
@@ -18,6 +20,8 @@ echo(sendPort) {
 }
 
 main() {
+  var function = funcFoo;
+
   ReceivePort port = new ReceivePort();
   Future spawn = Isolate.spawn(echo, port.sendPort);
   var caught_exception = false;
@@ -25,7 +29,7 @@ main() {
   asyncStart();
   stream.first.then((snd) {
     try {
-      snd.send(funcFoo);
+      snd.send(function);
     } catch (e) {
       caught_exception = true;
     }