Add first version of runAsync.

runtime/lib/event_loop_patch.dart

Index: runtime/lib/event_loop_patch.dart
diff --git a/tests/language/private_selector_lib.dart b/runtime/lib/event_loop_patch.dart
similarity index 54%
copy from tests/language/private_selector_lib.dart
copy to runtime/lib/event_loop_patch.dart
index c9a11c9b34ac40a3d631ffec1f16b497757e62f8..c4b25b7b2c628ad9b9f5186b675819135e572e34 100644
--- a/tests/language/private_selector_lib.dart
+++ b/runtime/lib/event_loop_patch.dart
@@ -2,18 +2,9 @@
 // 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 private_selector_lib;
-
-import 'private_selector_test.dart';
-
-bool executed = false;
-
-class A {
-  public() {
-    new B()._private();
-  }
-
-  _private() {
-    executed = true;
+patch class _AsyncRun {
+  /* patch */ static void _enqueueImmediate(void callback()) {
+    // TODO(9001): don't use the Timer to enqueue the immediate callback.
+    Timer.run(callback);
   }
 }