Test calling getPropertyValue on computed styles for -webkit-border-image property.

-webkit-box-reflect: right calc(50%);
  -webkit-box-reflect
    getPropertyValue:    right 50% none

-webkit-box-reflect: below calc(5px) -webkit-gradient(linear, 0 0, 0 0) 25 25 25 25 stretch stretch;
  -webkit-box-reflect
    getPropertyValue:    below 5px -webkit-gradient(linear, 0 0, 0 0) 25 fill / auto / 0px stretch