Implement scheduleImmediate for the VM.

runtime/lib/schedule_microtask_patch.dart

Index: runtime/lib/schedule_microtask_patch.dart
diff --git a/runtime/lib/schedule_microtask_patch.dart b/runtime/lib/schedule_microtask_patch.dart
index 75e87c8eb2fde52d0e0fa2e426e0a8478f0f2960..4ab593e05941abba9f783cfb11e2c762115d0fd4 100644
--- a/runtime/lib/schedule_microtask_patch.dart
+++ b/runtime/lib/schedule_microtask_patch.dart
@@ -2,24 +2,7 @@
 // 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.
 
-patch class _AsyncRun {
-  /* patch */ static void _scheduleImmediate(void callback()) {
-    if (_ScheduleImmediate._closure == null) {
-      // TODO(9001): don't default to using the Timer to enqueue the immediate
-      //             callback.
-      _createTimer(Duration.ZERO, callback);
-      return;
-    }
-    _ScheduleImmediate._closure(callback);
-  }
-}
-
-typedef void _ScheduleImmediateClosure(void callback());
-
-class _ScheduleImmediate {
-  static _ScheduleImmediateClosure _closure;
-}
-
-void _setScheduleImmediateClosure(_ScheduleImmediateClosure closure) {
-  _ScheduleImmediate._closure = closure;
+@deprecated
+void _setScheduleImmediateClosure(ScheduleImmediateClosure closure) {
+  scheduleImmediateClosure = closure;
 }