<!DOCTYPE html>

<style>
  body {
    width: 400px;
    height: 300px;
  }

  .flexbox {
    display: flex;
  }

  .column {
    flex-direction: column;
  }

  .flex11a {
    flex: 1 1 auto;
  }

  .root {
    height: 100px;
    overflow-y: auto;
  }
</style>


<p>This test should not have a horizontal scrollbar</p>

<div class="flexbox column">
  <div class="flexbox">
    <div class="flex11a">
      <div class="root">
        <div id="history"></div>
      </div>
    </div>
  </div>
</div>

<script>
onload = function() {
  var historyEl = document.getElementById('history');
  historyEl.offsetWidth;
  historyEl.innerText = '\n\n\n\n\n\n\n\n';
};
</script>