title: Clip-path not working with z-index
body: <p>I am having trouble placing a container on top of another container that uses a clipped-path. I have tried using z-index on either of the containers but it doesn't seem to help. </p>
  
  <p>If I remove the clipped-path class from the container then the block slides happily over the container. I have included <a href="https://jsfiddle.net/6jn6px4k/28/" rel="nofollow noreferrer">a fiddle of my problem.</a></p>
  
  <p>Here is my code:</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-js lang-js prettyprint-override"><code>window.onscroll = function(){
    var scrollTop = window.pageYOffset || document.documentElement.scrollTop;
    var para = Math.round(scrollTop / 1.2);
    document.querySelector('#block').style.transform = "translate3d(0px," + para + "px,0px)";
  }</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>body {margin: 5px;}
  
  #main {height:100vh;}
  #below-main {height:100vh;}
  #row1 {height:100vh;}
  
  
  /* Paralellogram to slide underneath block
  --------------------------------------------- */
  #bluestripe {  
    height: 60vh;
    width:60vw;
    margin: 0 auto;
  }
  
  img {width: 100%;}
  
  .clip-polygon {clip-path: polygon(100% 0, 100% 40%, 0 100%, 0 60%);}
  
  
  /* Block to sit above parallelogram
  --------------------------------------------- */
  #block {
    height: 50px;
    width:100px;
    margin: 50px auto 0 auto;
    transform: translate3d(0px,0px,0px);
    background-color: #999;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;body&gt;
    &lt;div id="main"&gt;
      &lt;div id="block"&gt;This needs to slide on top&lt;/div&gt;
        &lt;div id="bluestripe"&gt;
          &lt;img id="sea" src="https://images.pexels.com/photos/6644/sea-water-ocean-waves.jpg?w=940&amp;h=650&amp;auto=compress&amp;cs=tinysrgb" alt="" class="clip-polygon"&gt;
        &lt;/div&gt;
      &lt;div id="row1"&gt;&lt;/div&gt;   
    &lt;/div&gt;
  &lt;/body&gt;</code></pre>
  </div>
  </div>
  </p>