.waiting_modal {
    /*display:none;*/
    position:fixed;
    left:0;
    top:0;

    height: 5px;
    width: 100%;
    overflow: hidden;
    background-color: #ddd;
    z-index:10000;
}
.waiting_modal:before{
    display: block;
    position: absolute;
    content: "";
    left: -200px;
    width: 200px;
    height:inherit;
    background-color: blue;
    animation: loading 2s linear infinite;
}

@keyframes loading {
    from {left: -200px; width: 30%;}
    50% {width: 30%;}
    70% {width: 70%;}
    80% { left: 50%;}
    95% {left: 120%;}
    to {left: 100%;}
}