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.
break;
      case 115: 
        PDFViewerApplication.pdfSidebar.toggle();
        break;
    }
    if (
      turnPage !== 0 &&
      (!turnOnlyIfPageFit || pdfViewer.currentScaleValue === "page-fit")
    ) {
      if (turnPage > 0) {
        pdfViewer.nextPage();
      } else {
        pdfViewer.previousPage();
      }
      handled = true;
    }
  }
  
  if (cmd === 4) {
    switch (evt.keyCode) {
      case 13: 
      case 32: 
        if (
          !isViewerInPresentationMode &&
          pdfViewer.currentScaleValue !== "page-fit"
        ) {
          break;
        }
        if (PDFViewerApplication.page > 1) {
          PDFViewerApplication.page--;