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 moved = [],
    len = arr.length;
  let write = 0;
  for (let read = 0; read < len; ++read) {
    if (condition(arr[read])) {
      moved.push(arr[read]);
    } else {
      arr[write] = arr[read];
      ++write;
    }
  }
  for (let read = 0; write < len; ++read, ++write) {
    arr[write] = moved[read];
  }
}
/**
 * Get the active or focused element in current DOM.
 *
 * Recursively search for the truly active or focused element in case there are
 * shadow DOMs.
 *
 * @returns {Element} the truly active or focused element.
 */
function getActiveOrFocusedElement() {