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.
PDFViewerApplication.zoomOut();
        }
        handled = true;
        break;
      case 48: 
      case 96: 
        if (!isViewerInPresentationMode) {
          
          setTimeout(function () {
            
            PDFViewerApplication.zoomReset();
          });
          handled = false;
        }
        break;
      case 38: 
        if (isViewerInPresentationMode || PDFViewerApplication.page > 1) {
          PDFViewerApplication.page = 1;
          handled = true;
          ensureViewerFocused = true;
        }
        break;
      case 40: 
        if (
          isViewerInPresentationMode ||
          PDFViewerApplication.page < PDFViewerApplication.pagesCount
        ) {
          PDFViewerApplication.page = PDFViewerApplication.pagesCount;
          handled = true;
          ensureViewerFocused = true;