Add first version of runAsync.

runtime/lib/event_loop_patch.dart

Index: runtime/lib/event_loop_patch.dart
diff --git a/tests/compiler/dart2js_extra/deferred/deferred_class_library.dart b/runtime/lib/event_loop_patch.dart
similarity index 53%
copy from tests/compiler/dart2js_extra/deferred/deferred_class_library.dart
copy to runtime/lib/event_loop_patch.dart
index bf9a9dd5c760f3b7bff3acffa3cc9bb6ecc009f7..98e9bf2521a3bf195d1340ad5949b3f1813b36b6 100644
--- a/tests/compiler/dart2js_extra/deferred/deferred_class_library.dart
+++ b/runtime/lib/event_loop_patch.dart
@@ -2,13 +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.
 
-// Imported by deferred_class_test.dart.
-
-library deferred_class_library;
-
-class MyClass {
-  foo(x) {
-    print('MyClass.foo($x)');
-    return (x - 3) ~/ 2;
+patch class _AsyncRun {
+  /* patch */ static void _enqueueImmediate(void callback()) {
+    // TODO(floitsch): don't use the Timer to enqueue the immediate callback.
+    Timer.run(callback);
   }
 }