Fix new isolate_unhandled_exception tests to make them compatible for dartium testing.

tests/vm/dart/isolate_unhandled_exception_test2.dart

 // 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.
 
+library isolate_unhandled_exception_test2;
+
 import 'dart:isolate';
 import 'dart:io';
 
 // Tests that an isolate's keeps message handling working after
 // throwing an unhandled exception, if there is a top level callback
 // method that returns whether to continue handling messages or not.
 // This test verifies that a default-named callback function is called
 // when no callback is specified in Isolate.spawnFunction.
 
 // Note: this test will hang if an uncaught exception isn't handled,
@@ skipping 30 matching lines @@
       print('unhandled exception: ${future.exception}');
       exit(1);
     }
     if (future.value != 'hello') {
       print('unexpected response: ${future.value}');
       exit(1);
     }
     exit(0);
   });
 }