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.
},
  /**
   * Opens PDF document specified by URL or array with additional arguments.
   * @param {string|TypedArray|ArrayBuffer} file - PDF location or binary data.
   * @param {Object} [args] - Additional arguments for the getDocument call,
   *                          e.g. HTTP headers ('httpHeaders') or alternative
   *                          data transport ('range').
   * @returns {Promise} - Returns the promise, which is resolved when document
   *                      is opened.
   */
  async open(file, args) {
    if (this.pdfLoadingTask) {
      
      await this.close();
    }
    
    const workerParameters = AppOptions.getAll(OptionKind.WORKER);
    for (const key in workerParameters) {
      GlobalWorkerOptions[key] = workerParameters[key];
    }
    const parameters = Object.create(null);
    if (typeof file === "string") {
      
      this.setTitleUsingUrl(file);
      parameters.url = file;
    } else if (file && "byteLength" in file) {
      
      parameters.data = file;
    } else if (file.url && file.originalUrl) {
      this.setTitleUsingUrl(file.originalUrl);