code: function PDFPresentationMode_request() {
        if (this.switchInProgress || this.active ||
            !this.viewer.hasChildNodes()) {
          return false;
        }
        this._addFullscreenChangeListeners();
        this._setSwitchInProgress();
        this._notifyStateChange();
  
        if (this.container.requestFullscreen) {
          this.container.requestFullscreen();
        } else if (this.container.mozRequestFullScreen) {
          this.container.mozRequestFullScreen();
        } else if (this.container.webkitRequestFullscreen) {
          this.container.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
        } else if (this.container.msRequestFullscreen) {
          this.container.msRequestFullscreen();
        } else {
          return false;
        }
  
        this.args = {
          page: PDFViewerApplication.page,
          previousScale: PDFViewerApplication.currentScaleValue
        };
  
        return true;
      }
docs: Request the browser to enter fullscreen mode.
  @returns {boolean} Indicating if the request was successful.