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.
this.pdfRenderingQueue.printing = !!this.printService;
    this.pdfRenderingQueue.isThumbnailViewEnabled =
      this.pdfSidebar.isThumbnailViewVisible;
    this.pdfRenderingQueue.renderHighestPriority();
  },
  beforePrint() {
    
    
    this.pdfScriptingManager.dispatchWillPrint();
    if (this.printService) {
      
      
      
      return;
    }
    if (!this.supportsPrinting) {
      this.l10n.get("printing_not_supported").then(msg => {
        this._otherError(msg);
      });
      return;
    }