[html] Colspan/Rowspan for elements whose display is set to table-cell

I have the following code:

<div class="table">
    <div class="row">
        <div class="cell">Cell</div>
        <div class="cell">Cell</div>
    </div>
    <div class="row">
        <div class="cell colspan2">Cell</div>
    </div>
</div>

<style>
    .table {
        display: table;
    }
    .row {
        display: table-row;
    }
    .cell {
        display: table-cell;
    }
    .colspan2 {
        /* What to do here? */
    }
</style>

Pretty straightforward. How do I add a colspan (or the equivalent of colspan) for elements with display: table-cell?