css/css-cascade/layer-media-toggle.html

<!DOCTYPE html>
<title>CSS Cascade Layers: Tests against a Chrome bug that modifying a sheet affects existing layers</title>
<link rel="help" href="https://drafts.csswg.org/css-cascade-5/#layering">
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1313357">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<link rel="match" href="reference/ref-filled-green-100px-square.xht">

<style>
@layer foo, bar;
@layer bar {
  #target { background-color: green; }
}
@layer foo {
  #target { background-color: red; }
}
</style>
<style media="print" id="toggle">
#target {
  width: 100px;
  height: 100px;
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div id="target"></div>

<script>
document.body.offsetWidth; // Force style calculation
document.getElementById('toggle').media = 'all';
</script>