chromium/third_party/blink/web_tests/external/wpt/css/css-position/fixed-z-index-blend.html

<!DOCTYPE html>
<html class="reftest-wait" style="overflow-x:hidden;">
<title>fixed position, z-index, and mix-blend-mode</title>
<link rel="help" href="https://www.w3.org/TR/CSS2/visuren.html#fixed-positioning">
<link rel="help" href="https://www.w3.org/TR/CSS2/visuren.html#propdef-z-index">
<link rel="help" href="https://www.w3.org/TR/compositing-1/#mix-blend-mode">
<meta name="assert" content="Tests fixed, z-index, and mix-blend-mode.
Passes if there is a green box when the page is scrolled to the bottom.">
<link rel="author" href="mailto:[email protected]">
<link rel="match" href="fixed-z-index-blend-ref.html">

<div class="blend"></div>
<div class="background"></div>
<div class="text">
  <div style="width: 100px; height:4000px;"></div>
  <div style="background: green; width: 100px; height:100px;"></div>
</div>

<style>
.blend {
  display: block;
  position: fixed;
  z-index: 2;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  mix-blend-mode: overlay;
}

.background {
  pointer-events: none;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  opacity: 1;
}

.text {
  position: relative;
  z-index: 3;
  overflow: hidden;
  width: 100vw;
  min-height: 100vh;
  font-size: 50px;
  line-height: 2;
}
</style>

<script src="/common/reftest-wait.js"></script>
<script>
requestAnimationFrame(()=>{
  requestAnimationFrame(()=>{
    window.scrollBy(0, 4000);
    takeScreenshot();
  });
});
</script>
</html>