box-shadow on top of children

To avoid the use of an additional element, you can use css pseudo-elements. Try this demo.

#chatroom {
    position: relative;
}

#chatroom:before {
    content: "";

    /* Expand element */
    position: absolute;
    left: 0px;
    top: 0px;
    right: 0px;
    bottom: 0px;

    -moz-box-shadow: inset 0 0 8px rgba(0,0,0,.55);
    -webkit-box-shadow: inset 0 0 8px rgba(0,0,0,.55);
    box-shadow: inset 0 0 8px rgba(0,0,0,.55);

    /* Disable click events */
    pointer-events: none;
}

Basically this css creates that additional element for you. Notice the pointer-events:none to allow click events to pass through this element.

Keep in mind that pointer-events:none doesn’t work well on some mobile devices regarding touch scrolling (clicking/taping works well). I ended up not using inset shadows at all because of this.