message: [Improvement] reduce scroll utils
diff: @@ -12,7 +12,7 @@ function doBindEvent() {
  }
  this.el[CONTEXT].binded = true;
  - this.scrollEventListener = Utils.debounce(handleScrollEvent.bind(this), 200);
  + this.scrollEventListener = handleScrollEvent.bind(this);
  this.scrollEventTarget = Utils.getScrollEventTarget(this.el);
  const disabledExpr = this.el.getAttribute('waterfall-disabled');
  @@ -78,10 +78,8 @@ function handleScrollEvent() {
  function startBind(el) {
  const context = el[CONTEXT];
  - context.vm.$nextTick(function() {
  - if (Utils.isAttached(el)) {
  + context.vm.$nextTick(() => {
  doBindEvent.call(el[CONTEXT]);
  - }
  });
  }
  