<style>
@-webkit-keyframes x {
    100% {
        height: 0;

    }
}
div {
    width: 100%;
}

.inner {
    height: 100%;
    border: 1px solid lime;
    -webkit-animation-name: x;
    -webkit-animation-duration: 3s;
    -webkit-animation-iteration-count: infinite;
}

.outer {
    border: 1px solid red;
    height: 140px;
}

</style>


<div class=outer><div class=inner>
</div></div>