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
const location = evt.location,
    store = PDFViewerApplication.store;
  if (store && PDFViewerApplication.isInitialViewSet) {
    store
      .setMultiple({
        page: location.pageNumber,
        zoom: location.scale,
        scrollLeft: location.left,
        scrollTop: location.top,
        rotation: location.rotation,
      })
      .catch(function () {
        
      });
  }
  const href = PDFViewerApplication.pdfLinkService.getAnchorUrl(
    location.pdfOpenParams
  );
  PDFViewerApplication.appConfig.toolbar.viewBookmark.href = href;
  PDFViewerApplication.appConfig.secondaryToolbar.viewBookmarkButton.href = href;
  
  const currentPage = PDFViewerApplication.pdfViewer.getPageView(
     PDFViewerApplication.page - 1
  );
  const loading =
    (currentPage && currentPage.renderingState) !== RenderingStates.FINISHED;
  PDFViewerApplication.toolbar.updateLoadingIndicatorState(loading);
}
function webViewerScrollModeChanged(evt) {