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 currentScale = this._currentScale;
    const currentScaleValue = this._currentScaleValue;
    const normalizedScaleValue =
      parseFloat(currentScaleValue) === currentScale
        ? Math.round(currentScale * 10000) / 100
        : currentScaleValue;
    const pageNumber = firstPage.id;
    let pdfOpenParams = "#page=" + pageNumber;
    pdfOpenParams += "&zoom=" + normalizedScaleValue;
    const currentPageView = this._pages[pageNumber - 1];
    const container = this.container;
    const topLeft = currentPageView.getPagePoint(
      container.scrollLeft - firstPage.x,
      container.scrollTop - firstPage.y
    );
    const intLeft = Math.round(topLeft[0]);
    const intTop = Math.round(topLeft[1]);
    pdfOpenParams += "," + intLeft + "," + intTop;
    this._location = {
      pageNumber,
      scale: normalizedScaleValue,
      top: intTop,
      left: intLeft,
      rotation: this._pagesRotation,
      pdfOpenParams,
    };
  }
  _updateHelper(visiblePages) {