title: css property will-change undefined behaviour
body: <p>I am using semantic-ui, and have managed to narrow down some undefined behaviour in the css property <code>will-change</code> (I found it in their modal's):</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>.outer{
    background-color: black;
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
  }
  .inner{
    position:absolute;
    background-color: white;
    left: 50%;
    top: 100px;
    width: 400px;
    margin-left: -200px;
    height: 100px;
    padding: 5px;
    /**
     * comment out the line below
     * to see the desired/different result
     **/
    will-change: transform;
  }
  .baby{
    color: yellow;
    position: fixed;
    left: 20px;
    top: 20px;
    right: 0;
    border: 1px solid red;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="outer"&gt;
    &lt;div class="inner"&gt;
      &lt;div class="baby"&gt;here&lt;/div&gt;
      &lt;div class="content"&gt;some content&lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>I have only tested this in chrome. Does anyone have more information on what is going on here? Why does <code>will-change</code> do anything to the actual layout?</p>