windows pc微信内置浏览器h5网页鼠标滚动会触发 onmousewheel -> onblur -> onfocus

为什么鼠标滚动会触发 blur事件呢，然后又focus回来，而且频繁滚动 blur 和 focus 触发是无序的

与正常浏览器表现完全不一致

ua:

Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36 QBCore/4.0.1326.400 QQBrowser/9.0.2524.400 Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2875.116 Safari/537.36 NetType/WIFI MicroMessenger/7.0.20.1781(0x6700143B) WindowsWechat(0x63010200)