repress chrome mobile pull to refresh

preventToPullRefresh.js

window.addEventListener('load', function() {
  var maybePreventPullToRefresh = false;
  var lastTouchY = 0;
  document.addEventListener('touchstart', function(e) {
    if (e.touches.length != 1) return;
    lastTouchY = e.touches[0].clientY;
    // Pull-to-refresh will only trigger if the scroll begins when the
    // document's Y offset is zero.
    maybePreventPullToRefresh = window.pageYOffset == 0;
  }, false);
  
  document.addEventListener('touchmove', function(e) {
    var touchY = e.touches[0].clientY;
    var touchYDelta = touchY - lastTouchY;
    lastTouchY = touchY;

    if (maybePreventPullToRefresh) {
      // To suppress pull-to-refresh it is sufficient to preventDefault the
      // first overscrolling touchmove.
      maybePreventPullToRefresh = false;
      if (touchYDelta > 0) {
        e.preventDefault();
        return;
      }
    }
  }, false);
});