<!DOCTYPE html>
<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    internals.settings.setCSSVariablesEnabled(true);
}
</script>
<style>
div {
  -webkit-var-a: url(1);
  -webkit-mask: -webkit-var(a);
}
</style>
<div></div>
This test is successful if it does not crash.