message: Fix video thumbnailer
diff: @@ -237,7 +237,8 @@ function infoForImageFile(matrixClient, roomId, imageFile) {
  }
  /**
  - * Load a file into a newly created video element.
  + * Load a file into a newly created video element and pull some strings
  + * in an attempt to guarantee the first frame will be showing.
  *
  * @param {File} videoFile The file to load in an video element.
  * @return {Promise} A promise that resolves with the video image element.
  @@ -246,20 +247,25 @@ function loadVideoElement(videoFile): Promise<HTMLVideoElement> {
  return new Promise((resolve, reject) => {
  // Load the file into an html element
  const video = document.createElement("video");
  + video.preload = "metadata";
  + video.playsInline = true;
  + video.muted = true;
  const reader = new FileReader();
  reader.onload = function(ev) {
  - video.src = ev.target.result as string;
  -
  - // Once ready, returns its size
  // Wait until we have enough data to thumbnail the first frame.
  - video.onloadeddata = function() {
  + video.onloadeddata = async function() {
  resolve(video);
  + video.pause();
  };
  video.onerror = function(e) {
  reject(e);
  };
  +
  + video.src = ev.target.result as string;
  + video.load();
  + video.play();
  };
  reader.onerror = function(e) {
  reject(e);
  