<!DOCTYPE html>
<html>
<script>
if (window.internals)
    internals.settings.setCSSVariablesEnabled(true);
</script>
<style>
body {
    border-color: green;
    border-width: -webkit-var(a) -webkit-var(b) -webkit-var(c) -webkit-var(d);
    border-style: solid;
    -webkit-var-a: 1px;
    -webkit-var-b: 2px;
    -webkit-var-c: 3px;
    -webkit-var-d: 4px;
}
</style>
This text should be surrounded by a green border with 1px top, 2px right, 3px bottom, 4px left.
</html>