UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36

Example URL:
https://jsfiddle.net/sk2n36d0/2/

Steps to reproduce the problem:
1. Go to https://jsfiddle.net/sk2n36d0/2/ 
2. See that the content in the <th> element does not occupy the whole width of the <th> element

Markup and styles that are required to reproduce this issue:

<table>
<tr>
  <th colspan="2"><a>text</a><a>@</a></th>
</tr>
<tr>
  <th><a>text</a><a>@</a></th>
  <th><a>text</a><a>@</a></th>
</tr>
</table>

table {
  width:100%
}
a:first-child {
  background-color: red;
  width: 99%;
  display: table-cell;
}
a:last-child {
  background-color: green;
  width: 1%;
  display: table-cell;
}

What is the expected behavior?
Cell content occupies the whole width of the <th> element as it occurs in other browsers (checked in IE 11, Edge and Firefox). See the Output_Edge.PNG file.

What went wrong?
Content width is not adjusted (see the Output_Chrome.PNG screenshot)

Does it occur on multiple sites: N/A

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 66.0.3359.139  Channel: stable
OS Version: 10.0
Flash Version:
 

Deleted: Output_Chrome.PNG 2.6 KB

	Output_Chrome.PNG 2.6 KB View Download

Deleted: Output_Edge.PNG 2.6 KB

	Output_Edge.PNG 2.6 KB View Download