Add first version of runAsync.

tests/lib/async/run_async3_test.dart

+// Copyright (c) 2013, 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 run_async_test;
+
+import 'dart:async';
+import '../../../pkg/unittest/lib/unittest.dart';
+
+main() {
+  test("run async timer after async test", () {
+    // Check that Timers don't run before the async callbacks.
+    bool timerCallbackExecuted = false;
+
+    runAsync(expectAsync0(() {
+      Expect.isFalse(timerCallbackExecuted);
+    }));
+
+    Timer.run(expectAsync0(() { timerCallbackExecuted = true; }));
+
+    runAsync(expectAsync0(() {
+      Expect.isFalse(timerCallbackExecuted);
+    }));
+
+    // Busy loop.
+    var sum = 1;
+    var sw = new Stopwatch()..start();
+    while (sw.elapsedMilliseconds < 5) {
+      sum++;
+    }
+    if (sum == 0) throw "bad";  // Just to use the result.
+
+    runAsync(expectAsync0(() {
+      Expect.isFalse(timerCallbackExecuted);
+    }));
+  });
+}