Does not work in reader view (F9)

[badrazizi]

Unable to make it inject script into reader view, though it does show counter as been injected

URL pattern

about\:reader\?url=.*

code

(function shortCutSetter() {
  var previous = document.getElementsByClassName('narrate-skip-previous');
  if (previous.length > 0) {
    if (previous[0].getAttribute('accesskey') == null) {
      previous[0].setAttribute('accesskey', 'z');
    }
  }
  
  var playStop = document.getElementsByClassName('narrate-start-stop');
  if (playStop.length > 0) {
    if (playStop[0].getAttribute('accesskey') == null) {
      playStop[0].setAttribute('accesskey', 'x');
    }
  }
  
  var next = document.getElementsByClassName('narrate-skip-next');
  if (next.length > 0) {
    if (next[0].getAttribute('accesskey') == null) {
      next[0].setAttribute('accesskey', 'c');
    }
  }
})();