<!DOCTYPE html>
<html>
  <meta charset="utf-8">
  <title>CSS Reference: Dynamic change to the inline-size of a container containing a inline-flex child</title>
  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">

  <style>
  #container {
    border: 1px solid black;
    font: 30px monospace;
    width: 400px;
  }
  .inline-flex {
    display: inline-flex;
    width: 100px;
    border: 1px solid gray;
  }

  .small {
    display: flex;
    align-items: flex-end;
    font: 8px monospace;
    background: pink;
  }
  </style>

  <body>
    <div id="container">
      abc
      <div class="inline-flex">
        <div class="small">D</div>
        <div>efg</div>
      </div>
    </div>
  </body>
</html>