Speed up all media on page

speedup.js

function getAllMedia() {
  var getDocuments = function () {
    var f = function (document) {
      var iframes = Array.from(document.getElementsByTagName('iframe'));
      var result = [ document ];
      iframes.forEach(function (iframe) {
        var iframeDocument;
        try {
          iframeDocument = iframe.contentDocument;
        } catch (error) {
          return;
        }
        f(iframeDocument).forEach(function(d) { result.push(d); })
      });
      return result;
    };
    return f(window.document);
  }
  var media = [];
  getDocuments().forEach(function (d) {
    Array.from(d.getElementsByTagName('audio')).forEach(function (a) { media.push(a); });
    Array.from(d.getElementsByTagName('video')).forEach(function (v) { media.push(v); });
  });
  return media;
}

function speedAllUp(rate) {
  if (rate === undefined) {
    rate = 2.25;
  }
  if (window._speedAllUpInterval !== undefined) {
    clearInterval(window._speedAllUpInterval);
  }
  window._speedAllUpInterval = setInterval(function() {
    getAllMedia().forEach(function (m) { if (!m.paused && m.readyState >= 2) { m.playbackRate = rate; } });
  }, 100)
}

function normalPlaybackRate() {
  if (window._speedAllUpInterval !== undefined) {
    clearInterval(window._speedAllUpInterval);
    window._speedAllUpInterval = undefined;
  }
  getAllMedia().forEach(function (m) { m.playbackRate = 1; });
}