Use patching for dart:io.

runtime/bin/eventhandler_patch.dart

Index: runtime/bin/eventhandler_patch.dart
diff --git a/runtime/bin/eventhandler_patch.dart b/runtime/bin/eventhandler_patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f1e3a25c0ee059d227b4adb8ecd6e7df85cddfe6
--- /dev/null
+++ b/runtime/bin/eventhandler_patch.dart
@@ -0,0 +1,30 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// 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 _EventHandler {
+  /* patch */ static void _start() {
+    if (_eventHandler === null) {
+      _eventHandler = new _EventHandlerImpl();
+      _eventHandler._start();
+    }
+  }
+
+  /* patch */ static _sendData(Object sender,
+                               ReceivePort receivePort,
+                               int data) {
+    if (_eventHandler !== null) {
+      _eventHandler._sendData(sender, receivePort, data);
+    }
+  }
+
+  static _EventHandlerImpl _eventHandler;
+}
+
+
+class _EventHandlerImpl extends NativeFieldWrapperClass1 {
+  _EventHandlerImpl() { }
+  void _start() native "EventHandler_Start";
+  void _sendData(Object sender, ReceivePort receivePort, int data)
+      native "EventHandler_SendData";
+}