Fixed header cells with colspan get divided evenly.
</p>
<p class="error">Legacy chrome does not substract border spacing before distribution</p>
<table style="width:calc(300px + 40px)" data-expected-width=340>
  <tr>
    <td colspan=2 style="width:96px" data-expected-width=108>108</td>
    <td colspan=2 style="width:196px" data-expected-width=208>208</td>
  </tr>
  <tr>
    <td data-expected-width=50>1</td>
    <td>1</td>
    <td data-expected-width=100>1</td>
    <td>1</td>
  </tr>
</table>

<p 13 class="