<style>
    div {
        width: 100px;
        height: 100px;
    }
    .container {
        position: absolute;
        top: 100px;
    }
    #contains-paint {
        contain: paint;
    }
    #has-transform {
        will-change: transform;
    }
    .fixed {
        position: fixed;
        top: 0;
    }
    .spacer {
        height: 2000px;
    }
</style>
<script>
onload = function() {
    window.scrollTo(0, 50);
};
</script>
<div class="container" id="simple-container"><div id="fixed1" class="fixed"></div></div>
<div class="container" id="has-transform"><div id="fixed2" class="fixed"></div></div>
<div class="container" id="contains-paint"><div id="fixed3" class="fixed"></div></div>
<div class="spacer"></div>