Support Dart 1.8.0.

lib/src/dart.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 unittest.dart;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
@@ skipping 18 matching lines @@
   new File(dartPath).writeAsStringSync(code);
   var port = new ReceivePort();
   return Isolate.spawn(_isolateBuffer, {
     'replyTo': port.sendPort,
     'uri': p.toUri(dartPath).toString(),
     'packageRoot': packageRoot == null ? null : packageRoot.toString(),
     'message': message
   }).then((isolate) {
     return port.first.then((response) {
       if (response['type'] != 'error') return isolate;
-      isolate.kill();
+      if (supportsIsolateKill) isolate.kill();
       var asyncError = RemoteException.deserialize(response['error']);
       return new Future.error(asyncError.error, asyncError.stackTrace);
     });
   }).catchError((error) {
     new Directory(dir).deleteSync(recursive: true);
     throw error;
   }).then((isolate) {
     return new IsolateWrapper(isolate,
         () => new Directory(dir).deleteSync(recursive: true));
   });
@@ skipping 12 matching lines @@
   Isolate.spawnUri(Uri.parse(message['uri']), [], message['message'],
           packageRoot: packageRoot)
       .then((_) => replyTo.send({'type': 'success'}))
       .catchError((error, stackTrace) {
     replyTo.send({
       'type': 'error',
       'error': RemoteException.serialize(error, stackTrace)
     });
   });
 }