Move isolate tests to lib/isolate.

tests/lib/async/timer_isolate_test.dart

-// Copyright (c) 2012, 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 multiple_timer_test;
-
-import 'dart:isolate';
-import 'dart:async';
-import 'package:unittest/unittest.dart';
-
-const Duration TIMEOUT = const Duration(milliseconds: 100);
-
-// Some browsers (Firefox and IE so far) can trigger too early. Add a safety
-// margin. We use identical(1, 1.0) as an easy way to know if the test is
-// compiled by dart2js.
-int get safetyMargin => identical(1, 1.0) ? 100 : 0;
-
-createTimer(replyTo) {
-  new Timer(TIMEOUT, () {
-    replyTo.send("timer_fired");
-  });
-}
-
-main() {
-  test("timer in isolate", () {
-    int startTime;
-    int endTime;
-
-    ReceivePort port = new ReceivePort();
-
-    port.first.then(expectAsync((msg) {
-      expect("timer_fired", msg);
-      int endTime = (new DateTime.now()).millisecondsSinceEpoch;
-      expect(endTime - startTime + safetyMargin, greaterThanOrEqualTo(TIMEOUT.inMilliseconds));
-    }));
-
-    startTime = (new DateTime.now()).millisecondsSinceEpoch;
-    var remote = Isolate.spawn(createTimer, port.sendPort);
-  });
-}