title: position: sticky not working in firefox
body: <p>position:sticky is said to be working in firefox but I'm not seeing my sidebar stick.</p>
  
  <p>My html looks like this:</p>
  
  <pre><code>&lt;div class="wrap"&gt;
  
      &lt;div class="sticky"&gt;side &lt;/div&gt;    
      &lt;div class="content"&gt;content &lt;div&gt;
  &lt;div&gt;
  </code></pre>
  
  <p>My css:</p>
  
  <pre><code>.content{
      height: 2000px;
      overflow: hidden;
  }
  
  .sticky{
      position: sticky;
      width: 200px;
      float: left;
  }
  </code></pre>
  
  <p>As I scroll down the sidebar scrolls with the content. It doesn't stick. Anyone know what could be the issue?</p>