code: function pdfViewClose() {
            var errorWrapper = this.appConfig.errorWrapper.container;
            errorWrapper.setAttribute('hidden', 'true');
            if (!this.pdfLoadingTask) {
              return Promise.resolve();
            }
            var promise = this.pdfLoadingTask.destroy();
            this.pdfLoadingTask = null;
            if (this.pdfDocument) {
              this.pdfDocument = null;
              this.pdfThumbnailViewer.setDocument(null);
              this.pdfViewer.setDocument(null);
              this.pdfLinkService.setDocument(null, null);
            }
            this.store = null;
            this.isInitialViewSet = false;
            this.pdfSidebar.reset();
            this.pdfOutlineViewer.reset();
            this.pdfAttachmentViewer.reset();
            this.findController.reset();
            this.findBar.reset();
            if (typeof PDFBug !== 'undefined') {
              PDFBug.cleanup();
            }
            return promise;
          }
docs: Closes opened PDF document.
  @returns {Promise} - Returns the promise, which is resolved when all
  destruction is completed.