Add an "onPlatform" parameter to test() and group().

lib/src/runner/vm/isolate_test.dart

 // Copyright (c) 2015, 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 test.runner.vm.isolate_test;
 
 import 'dart:async';
 import 'dart:isolate';
 
 import '../../backend/live_test.dart';
 import '../../backend/live_test_controller.dart';
 import '../../backend/metadata.dart';
 import '../../backend/state.dart';
 import '../../backend/suite.dart';
 import '../../backend/test.dart';
 import '../../util/remote_exception.dart';
 
 /// A test in another isolate.
-class IsolateTest implements Test {
+class IsolateTest extends Test {
   final String name;
   final Metadata metadata;
 
   /// The port on which to communicate with the remote test.
   final SendPort _sendPort;
 
   IsolateTest(this.name, this.metadata, this._sendPort);
 
   /// Loads a single runnable instance of this test.
   LiveTest load(Suite suite) {
@@ skipping 44 matching lines @@
       // If the test is still running, send it a message telling it to shut down
       // ASAP. This causes the [Invoker] to eagerly throw exceptions whenever
       // the test touches it.
       sendPortCompleter.future.then((sendPort) {
         sendPort.send({'command': 'close'});
         return controller.completer.future;
       }).then((_) => receivePort.close());
     });
     return controller.liveTest;
   }
+
+  Test change({String name, Metadata metadata}) {
+    if (name == null) name = this.name;
+    if (metadata == null) metadata = this.metadata;
+    return new IsolateTest(name, metadata, _sendPort);
+  }
 }