title: Popper not sticking to ref element on scroll
body: <p>Demo: <a href="https://codesandbox.io/s/agitated-euler-rep54" rel="nofollow noreferrer">https://codesandbox.io/s/agitated-euler-rep54</a></p>
  
  <p>Click on any "click me to set ref". The popper correctly positions itself. Now start scrolling, and you'll see the popper doesn't stick to the ref.</p>
  
  <p>If you move <code>.popper</code> to be a direct child of <code>.scroll-body</code>, it works.</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;div id="app"&gt;
      &lt;div class="scroll-body"&gt;
        &lt;div v-for="n in 40"&gt;
            &lt;span @click="setRef" class="ref"&gt;
              click me to set ref
            &lt;/span&gt;
        &lt;/div&gt;
      &lt;/div&gt;
      &lt;div ref="popper" class="popper"&gt;popper&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>What popper option do I need to set to make it work?</p>