title: How do i make a fieldset `display: block; overflow: auto` show a scrollbar?
body: <p>I want my <code>&lt;fieldset&gt;</code> elements to behave like vanilla <code>&lt;div&gt;</code>'s by filling their containing element and showing a scrollbar when they are set to <code>overflow: auto</code>.</p>
  
  <p>For instance, I don't see why the fieldset in <a href="http://codepen.io/aaronj1335/pen/JEFmi" rel="nofollow">this
  example</a> is wider than its containing div:</p>
  
  <pre><code>&lt;div class=outer&gt;
    &lt;fieldset class=inner&gt;
        fooooooooooooooooooooooooooooooooooooo
    &lt;/fieldset&gt;
  &lt;/div&gt;
  
  &lt;div class=outer&gt;
    &lt;div class=inner&gt;
      fooooooooooooooooooooooooooooooooooooooo
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and corresponding css:</p>
  
  <pre><code>.outer {
    width: 60px;
  }
  
  .inner {
    overflow: auto;
    display: block;
    height: 60px;
    border: 1px solid red;
  }
  </code></pre>