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.
downloadManager: null,
  
  overlayManager: null,
  
  preferences: null,
  
  toolbar: null,
  
  secondaryToolbar: null,
  
  eventBus: null,
  
  l10n: null,
  isInitialViewSet: false,
  downloadComplete: false,
  isViewerEmbedded: window.parent !== window,
  url: "",
  baseUrl: "",
  externalServices: DefaultExternalServices,
  _boundEvents: Object.create(null),
  documentInfo: null,
  metadata: null,
  _contentDispositionFilename: null,
  _contentLength: null,
  _saveInProgress: false,
  _wheelUnusedTicks: 0,
  _idleCallbacks: new Set(),
  
  async initialize(appConfig) {