test/e2e/resources/elements/css-variables.html

<!--
  Copyright 2020 The Chromium Authors
  Use of this source code is governed by a BSD-style license that can be
  found in the LICENSE file.
-->
<!DOCTYPE html>
<style>
  html {
    --color: black;
    --title-color: var(--color);
    --move-final-width: 100%;
  }

  body, body {
    --color: white;
  }

  #properties-to-inspect {
    color: var(--title-color);
  }

  #keyframes-rule {
    animation: move;
  }

  @keyframes move {
    from {
      width: 0%;
    }

    to {
      width: var( --move-final-width);
    }
  }
</style>
<div id="properties-to-inspect"></div>
<div id="keyframes-rule"></div>