Make IsolateWrapper compatible with the 1.11 isolate API changes.

test/runner/isolate_listener_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.
 
 @TestOn("vm")
 
 import 'dart:async';
 import 'dart:isolate';
 
 import 'package:test/src/backend/invoker.dart';
@@ skipping 15 matching lines @@
 Isolate _isolate;
 
 /// A live test that's running for the current test.
 ///
 /// This is tracked so that it can be closed once the test is done.
 LiveTest _liveTest;
 
 void main() {
   tearDown(() {
     if (_isolate != null && supportsIsolateKill) {
-      _isolate.kill(Isolate.IMMEDIATE);
+      _isolate.kill();
     }
     _isolate = null;
 
     if (_liveTest != null) _liveTest.close();
     _liveTest = null;
   });
 
   test("sends a list of available tests on startup", () {
     return _spawnIsolate(_successfulTests).then((receivePort) {
       return receivePort.first;
@@ skipping 346 matching lines @@
 /// An isolate entrypoint that defines a test that prints twice.
 void _printTest(SendPort sendPort) {
   IsolateListener.start(sendPort, () => () {
     test("prints", () {
       print("Hello,");
       return new Future(() => print("world!"));
     });
   });
 }