title: document.documentElement.style.setProperty('--some-color', 'green') does not work in IE
body: <p>I have a custom css variable declared in a separate css file in a selector.</p>
  
  <pre><code>.ui-grid-row:nth-child(odd) {
  background-color: var(--altbg-color) !important;
  }
  </code></pre>
  
  <p>This is not a root element. So not sure how css-vars-ponyfill will work in this case. I have tried that too but could not make it work. (I would be grateful if somebody can help me make it work.)</p>
  
  <p>I am trying to set value to the variable through javascript (I am using AngularJS 1.3) using </p>
  
  <pre><code>document.documentElement.style.setProperty('--some-color', 'green')
  </code></pre>
  
  <p>which works fine with Chrome &amp; Firefox but not in  IE(11).</p>
  
  <p>Does anybody have a solution?</p>
  
  <p>Thanks in advance.</p>