<!DOCTYPE html>
<script>
onload = function() {
  window.scrollTo(0, 400);
};
</script>
<style>
body {
  height: 2000px;
}
#fixed-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: green;
  backface-visibility: hidden;
}
</style>
Tests paint invalidation of fixed elements under a composited fixed element after scrolled.
Passes if there is only green background.
<div id="fixed-container">
</div>