<!DOCTYPE html> <!-- webkit-test-runner [ LayoutFormattingContextEnabled=true LayoutFormattingContextIntegrationEnabled=false ] -->
<style>
table {
    border: 10px solid green;
}

th {
    width: 20px;
    height: 20px;
}

thead {
    border: 50px solid red;
}
</style>
<table>
<thead>
<tr><th></th><th></th></tr>
<tr><th></th><th></th></tr>
</thead>
</table>