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
throw new Error(
            "Deprecated parameter: `active`, please use `state` instead."
          );
        },
        get switchInProgress() {
          throw new Error(
            "Deprecated parameter: `switchInProgress`, please use `state` instead."
          );
        },
      });
    }
  }
  /**
   * Used to initialize a timeout when requesting Presentation Mode,
   * i.e. when the browser is requested to enter fullscreen mode.
   * This timeout is used to prevent the current page from being scrolled
   * partially, or completely, out of view when entering Presentation Mode.
   * NOTE: This issue seems limited to certain zoom levels (e.g. page-width).
   *
   * @private
   */
  _setSwitchInProgress() {