<script>
internals.settings.setCSSVariablesEnabled(true);
</script>
<style>
div {
  border-color: green;
  border-style: solid;
  border-width: -webkit-var(a) -webkit-var(b);
  -webkit-var-a: 3px;
  -webkit-var-b: 10px
}
</style>
<div>This text should have top and bottom borders of 3px and left and right borders of 10px</div>