Make IsolateWrapper compatible with the 1.11 isolate API changes.

lib/src/runner/loader.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.loader;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
@@ skipping 27 matching lines @@
   /// The package root to use for loading tests, or `null` to use the automatic
   /// root.
   final String _packageRoot;
 
   /// The URL for the `pub serve` instance to use to load tests.
   ///
   /// This is `null` if tests should be loaded from the filesystem.
   final Uri _pubServeUrl;
 
   /// All isolates that have been spun up by the loader.
-  final _isolates = new Set<Isolate>();
+  final _isolates = new Set<IsolateWrapper>();
 
   /// The server that serves browser test pages.
   ///
   /// This is lazily initialized the first time it's accessed.
   Future<BrowserServer> get _browserServer {
     if (_browserServerCompleter == null) {
       _browserServerCompleter = new Completer();
       BrowserServer.start(
               root: _root,
               packageRoot: _packageRoot,
@@ skipping 163 matching lines @@
   Future close() {
     for (var isolate in _isolates) {
       isolate.kill();
     }
     _isolates.clear();
 
     if (_browserServerCompleter == null) return new Future.value();
     return _browserServer.then((browserServer) => browserServer.close());
   }
 }