Move isolate tests to lib/isolate.

tests/lib/async/stream_controller_async_test.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.
 
 // Test the basic StreamController and StreamController.broadcast.
 library stream_controller_async_test;
 
 import 'dart:async';
-import 'dart:isolate';
 import "package:expect/expect.dart";
 import 'package:unittest/unittest.dart';
 import 'event_helper.dart';
 import 'stream_state_helper.dart';
 
 void cancelSub(StreamSubscription sub) { sub.cancel(); }
 
 testController() {
   // Test fold
   test("StreamController.fold", () {
@@ skipping 743 matching lines @@
   testRethrow();
   testBroadcastController();
   testAsBroadcast();
   testSink(sync: true, broadcast: false, asBroadcast: false);
   testSink(sync: true, broadcast: false, asBroadcast: true);
   testSink(sync: true, broadcast: true, asBroadcast: false);
   testSink(sync: false, broadcast: false, asBroadcast: false);
   testSink(sync: false, broadcast: false, asBroadcast: true);
   testSink(sync: false, broadcast: true, asBroadcast: false);
 }