<!DOCTYPE HTML>
<style>
#container {
  display: flex;
  align-items: flex-start;
  width: 200px;
  height: 300px;
  background-color: red;
}
.item {
  background-color: green;
  border: solid thin blue;
  width: 100px;
  height: 300px;
}
</style>
<p style="height: 20px">There should be no invalidations because align-content style change causes no visual change.</p>
<div id="container">
  <div class="item"></div>
  <div class="item"></div>
</div>