Implement scheduleImmediate for the VM.

sdk/lib/_internal/lib/async_patch.dart

Index: sdk/lib/_internal/lib/async_patch.dart
diff --git a/sdk/lib/_internal/lib/async_patch.dart b/sdk/lib/_internal/lib/async_patch.dart
index 8d6bb2639ec86d42d01c8aec9eb51ff02a66832e..ddf16e3f31a4eda31ef543ca9984c775872a7ad6 100644
--- a/sdk/lib/_internal/lib/async_patch.dart
+++ b/sdk/lib/_internal/lib/async_patch.dart
@@ -21,13 +21,6 @@ patch Timer _createPeriodicTimer(Duration duration,
   return new TimerImpl.periodic(milliseconds, callback);
 }
 
-patch class _AsyncRun {
-  patch static void _scheduleImmediate(void callback()) {
-    // TODO(9002): don't use the Timer to enqueue the immediate callback.
-    _createTimer(Duration.ZERO, callback);
-  }
-}
-
 patch class DeferredLibrary {
   patch Future<bool> load() {
     return _load(libraryName, uri);