Implement automatic loading of dart:core_native_fields library

bin/eventhandler.dart

Index: bin/eventhandler.dart
===================================================================
--- bin/eventhandler.dart	(revision 1520)
+++ bin/eventhandler.dart	(working copy)
@@ -2,6 +2,11 @@
 // 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.
 
+// Create an empty class to represent the native fields used in
+// the EventHandler class (it needs one native field).
+class EventHandlerNativeWrapper extends NativeFieldWrapperClass1 {
+}
+
 class EventHandler extends EventHandlerNativeWrapper {
   EventHandler() { }