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.eventBus.dispatch("fileinputchange", {
        source: this,
        fileInput: evt.target,
      });
    });
    
    appConfig.mainContainer.addEventListener("dragover", function (evt) {
      evt.preventDefault();
      evt.dataTransfer.dropEffect = "move";
    });
    appConfig.mainContainer.addEventListener("drop", function (evt) {
      evt.preventDefault();
      const files = evt.dataTransfer.files;
      if (!files || files.length === 0) {
        return;
      }
      PDFViewerApplication.eventBus.dispatch("fileinputchange", {
        source: this,
        fileInput: evt.dataTransfer,
      });
    });
  } else {
    appConfig.toolbar.openFile.hidden = true;
    appConfig.secondaryToolbar.openFileButton.hidden = true;
  }
  if (!PDFViewerApplication.supportsDocumentFonts) {
    AppOptions.set("disableFontFace", true);
    PDFViewerApplication.l10n.get("web_fonts_disabled").then(msg => {
      console.warn(msg);
    });