#info-box {
    position: relative;
    box-sizing: border-box;
    overflow: auto;
    background: #fdfdfd;
    height: 100px;       /* initial height */
    min-height: 50px;    /* tweak as you like */
}
#info-box .resizer {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 12px;         /* the drag handle area */
    cursor: ns-resize;
    background: transparent;
}
#info-box .resizer:hover {
    background: rgba(0,0,0,0.05);
}