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.
AutomationEventBus,
  AutoPrintRegExp,
  DEFAULT_SCALE_VALUE,
  EventBus,
  getActiveOrFocusedElement,
  isValidRotation,
  isValidScrollMode,
  isValidSpreadMode,
  MAX_SCALE,
  MIN_SCALE,
  noContextMenuHandler,
  normalizeWheelEventDirection,
  parseQueryString,
  ProgressBar,
  RendererType,
  ScrollMode,
  SidebarView,
  SpreadMode,
  TextLayerMode,
} from "./ui_utils.js";
import { AppOptions, compatibilityParams, OptionKind } from "./app_options.js";
import {
  build,
  createPromiseCapability,
  getDocument,
  getFilenameFromUrl,
  getPdfFilenameFromUrl,
  GlobalWorkerOptions,
  InvalidPDFException,
  isPdfFile,