Drag and drop issue

gistfile1.txt

import 'dart:html';

void main() {
  query("#text")
    ..text = "Click me!";

  // Works when compiled to JS
  query("#container")
    ..on.drop.add(reverseText);
}

void reverseText(Event event) {
  event.stopPropagation();
  event.preventDefault();
  var text = query("#text").text;
  var buffer = new StringBuffer();
  for (int i = text.length - 1; i >= 0; i--) {
    buffer.add(text[i]);
  }
  query("#text").text = buffer.toString();
}