<!DOCTYPE HTML>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api/#dom-css-registerproperty" />
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1899272">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id=element></div>
<script>
test(function() {
  CSS.registerProperty({
    name: '--length-calc',
    syntax: '<length>',
    initialValue: '0px',
    inherits: true
  });
  CSS.registerProperty({
 