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.
/* Copyright 2013 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import { createObjectURL, createValidAbsoluteUrl, isPdfFile } from "pdfjs-lib";
import { compatibilityParams } from "./app_options.js";
if (typeof PDFJSDev !== "undefined" && !PDFJSDev.test("CHROME || GENERIC")) {
  throw new Error(
    'Module "pdfjs-web/download_manager" shall not be used ' +
      "outside CHROME and GENERIC builds."
  );
}
function download(blobUrl, filename) {