isolates refactor: this change introduces 'dart:isolate' as a library. This is a

tests/isolate/src/MessageTest.dart

 // Copyright (c) 2011, 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.
 
 // Dart test program for testing serialization of messages.
 // VMOptions=--enable_type_checks --enable_asserts
 
 #library('MessageTest');
+#import("dart:isolate");
 #import("TestFramework.dart");
 
 // ---------------------------------------------------------------------------
 // Message passing test.
 // ---------------------------------------------------------------------------
 
 class MessageTest {
   static void test(TestExpectation expect) {
     PingPongClient.test(expect);
   }
@@ skipping 118 matching lines @@
             replyTo.send(message, null);
             count++;
           }
         });
   }
 }
 
 main() {
   runTests([MessageTest.test]);
 }