title: Prevent grid area from expanding causing whole page to scroll
body: <p>I'm using the following grid layout:</p>
  
  <pre><code>grid-template-columns: 10em 1fr 10em;
  grid-template-rows: 2em 1fr 2em;
  </code></pre>
  
  <p>To create a centered area that fills most of the screen while leaving some padding around it. Inside this <code>1fr x 1fr</code> grid area is a <code>pane</code> div which contains an <code>editor</code> div which contains a <code>content</code> div.</p>
  
  <p>The <code>content</code> div can be any height, and the <code>editor</code> div has <code>overflow: scroll</code> set. My problem is that instead of <code>pane</code> staying the same size and <code>editor</code> handling the overflow, <code>pane</code> grows and causes the whole page to scroll.</p>
  
  <p>I can keep <code>pane</code> from growing by setting its <code>overflow: scroll</code>, but this causes the editor itself to scroll, rather than its content. This is unacceptable because the editor has buttons which must always be on screen.</p>
  
  <p>Is there a way, within grid layout, to allow this functionality? I originally had it working with a flex layout, where the <code>pane</code> div was a single item within a <code>100% x 100%</code> flexbox. I switched to grid to allow me to easily resize side-menus, so implementing this without grid is not preferable. </p>
  
  <p>Also, multi-browser support would be amazing, but my target browser is Chrome.</p>
  
  <p><a href="https://jsfiddle.net/aqd8vrtf/2/" rel="noreferrer">Here's a jsfiddle with my reproducing my problem.</a></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>body, html {
    width: 100%;
    height: 100%;
    padding: 0;
    margin: 0;
  }
  
  #site {
    width: 100%;
    height: 100%;
    background-color: #000;
    
    display: grid;
    grid-template-rows: 10em 1fr 10em;
    grid-template-columns: 2em 1fr 2em;
    grid-template-areas:
    'top top top'
    'lpn mid rpn'
    'bot bot bot';
  }
  
  #pane {
    grid-area: mid;
    height: 100%;
    width: 100%;
    background-color: #f0f;
  }
  
  #editor {
    display: relative;
    overflow: scroll;
  }
  
  #content {
     height: 2000px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id='site'&gt;
  &lt;div id='pane'&gt;
    &lt;div id='editor'&gt;
      &lt;div id='content'&gt;  
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>