Bookmarklet to uncripple Kindle Cloud Reader

gistfile1.js

(function() {
  function uncrippleFrame() {
    var body = this.contentWindow.document.getElementsByTagName('body')[0];

    this.contentWindow.onclick = null;
    body._frame = this;

    body.onmousemove = function() {
      this._frame.contentWindow.onclick = null;
      this.setAttribute('style', '-webkit-user-select: auto;');
      this.oncontextmenu = body.onselectstart = null;
    };
    body.onmousemove();
  };

  var container = document.getElementsByTagName('iframe')[0].contentWindow;
  var frames = container.document.getElementsByTagName('iframe');

  for (var i = 0; i < frames.length; i++) {
    uncrippleFrame.call(frames[i]);
    frames[i].onload = uncrippleFrame;
  }
})();

Just tried it with Safari 5.1.4 on my Mac and it doesn't work at all. No errors in the dev console either.