This problem applies to all the documents that I have ever opened.

Configuration:
- Web browser and its version: Google Chrome 83.0.4103.61 , also Firefox 76.0.1
- Operating system and its version: Win 7 x64
- PDF.js version: 2.3.164 version of extension
- Is a browser extension: yes

Steps to reproduce the problem:
1. Select any "Spreads" mode of view. Or "No spreads", but wrapped scrolling mode - doesn't matter. 
2. Select "Page Fit" zoom mode. We should get several pages per screen
3. Try to scroll document by any of keys: Page Down, n, j, Space Bar

I expect to see the next group of pages (for example, if there are 5 pages on the screen, I expect to see the next 5 pages)

What went wrong? Scrolling goes one page at a time, so if I have 5 pages on the screen, nothing happens when I pressed Page Down 5 times . For the 6th time I finally see the next group of pages.

Just for example: Adobe Reader scrolls properly in two-page mode, 2 pages at once. 

P.S. Sorry for my English, I hope I correctly stated the essence of the problem
} else if (PDFJSDev.test("CHROME")) {
      baseDocumentUrl = location.href.split("#")[0];
    }
    this.pdfLinkService.setDocument(pdfDocument, baseDocumentUrl);
    this.pdfDocumentProperties.setDocument(pdfDocument, this.url);
    const pdfViewer = this.pdfViewer;
    pdfViewer.setDocument(pdfDocument);
    const { firstPagePromise, onePageRendered, pagesPromise } = pdfViewer;
    const pdfThumbnailViewer = this.pdfThumbnailViewer;
    pdfThumbnailViewer.setDocument(pdfDocument);
    const storedPromise = (this.store = new ViewHistory(
      pdfDocument.fingerprint
    ))
      .getMultiple({
        page: null,
        zoom: DEFAULT_SCALE_VALUE,
        scrollLeft: "0",
        scrollTop: "0",
        rotation: null,
        sidebarView: SidebarView.UNKNOWN,
        scrollMode: ScrollMode.UNKNOWN,
        spreadMode: SpreadMode.UNKNOWN,
      })
      .catch(() => {
        
        return Object.create(null);
      });
    firstPagePromise.then(pdfPage => {
      this.loadingBar.setWidth(this.appConfig.viewerContainer);
      this._initializeAnnotationStorageCallbacks(pdfDocument);