title: Single line (shorthand) background style?
body: <p>I'm following this guide: <a href="http://www.w3schools.com/cssref/css3_pr_background.asp" rel="nofollow">CSS background Property</a>.</p>
  
  <pre class="lang-css prettyprint-override"><code>background: color image position/size repeat origin clip attachment initial|inherit;
  </code></pre>
  
  <p>I have this background CSS:</p>
  
  <pre class="lang-css prettyprint-override"><code>background-color: grey;
  background-repeat: no-repeat;
  background-size: contain;
  background-position: center;
  background-origin: content-box;
  </code></pre>
  
  <p>I'm trying to convert it to one line:</p>
  
  <pre class="lang-css prettyprint-override"><code>background: grey center / contain no-repeat content-box;
  </code></pre>
  
  <p>I need the background image and grey to be the background of the padding too.</p>
  
  <p>Where am I going wrong?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>div{
      width: 200px;
      height: 400px;
      background: grey center / contain no-repeat content-box;
      padding: 30px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div style="background-image: url(https://upload.wikimedia.org/wikipedia/en/5/50/NES_Super_Mario_Bros.png)"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p><a href="https://jsfiddle.net/asgs4zdh/" rel="nofollow">JSFiddle</a></p>