STR:
  - Go to https://mozilla.github.io/pdf.js/web/viewer.html
  - Click on "Open File" and open a pdf

The `Download` button and the `Current view` one just disappear.
I can reproduce this bug with Firefox nightly, Chrome stable and Epiphany on debian.
constructor() {
    this._openBlobUrls = new WeakMap();
  }
  downloadUrl(url, filename) {
    if (!createValidAbsoluteUrl(url, "http://example.com")) {
      return; 
    }
    download(url + "#pdfjs.action=download", filename);
  }
  downloadData(data, filename, contentType) {
    const blobUrl = createObjectURL(
      data,
      contentType,
      compatibilityParams.disableCreateObjectURL
    );
    download(blobUrl, filename);
  }
  /**
   * @returns {boolean} Indicating if the data was opened.
   */
  openOrDownloadData(element, data, filename) {