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.
eventBus,
      this.l10n
    );
    this.pdfCursorTools = new PDFCursorTools({
      container,
      eventBus,
      cursorToolOnLoad: AppOptions.get("cursorToolOnLoad"),
    });
    this.toolbar = new Toolbar(appConfig.toolbar, eventBus, this.l10n);
    this.secondaryToolbar = new SecondaryToolbar(
      appConfig.secondaryToolbar,
      container,
      eventBus
    );
    if (this.supportsFullscreen) {
      this.pdfPresentationMode = new PDFPresentationMode({
        container,
        pdfViewer: this.pdfViewer,
        eventBus,
      });
    }
    this.passwordPrompt = new PasswordPrompt(
      appConfig.passwordOverlay,
      this.overlayManager,
      this.l10n,
      this.isViewerEmbedded
    );
    this.pdfOutlineViewer = new PDFOutlineViewer({
      container: appConfig.sidebar.outlineView,
      eventBus,