LayoutTests/fast/css/root-container-back-forward.html

<!-- webkit-test-runner [ UsesBackForwardCache=true ] -->
<style>
:root {
  container: root / inline-size;
}
@container root (width >= 100px) {
  div { color: green }
}
</style>
<div>Green</div>
<script>
testRunner.queueLoad("about:blank");
testRunner.queueBackNavigation(1);
</script>