一个元素连续执行多个动画

示例：
.demo {
    -webkit-animation-name: bounceInLeft1, bounce1;
    -webkit-animation-duration: 2s, 1.5s;
    -webkit-animation-timing-function: ease, linear;
    -webkit-animation-delay: 5.2s, 7.2s;
    -webkit-animation-iteration-count: 1, infinite;
    -webkit-animation-fill-mode: forwards, none;
   
    animation-name: bounceInLeft1, bounce1;
    animation-duration: 2s, 1.5s;
    animation-timing-function: ease, linear;
    animation-delay: 5.2s, 7.2s;
    animation-iteration-count: 1, infinite;
    animation-fill-mode: forwards, none;
}

原理：同时设置多个动画，利用延时实现动画效果