title: SMIL animation doesn't work on a use element on Firefox
body: <p>Although this animation is working on Chrome, Safary and Opera, it doesn't work on Firefox when I'm using the group:</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>svg {
    max-width: 90vh;
    stroke-linecap: round;
    display:block;
    position:absolute;
    margin:auto;
    top:0;bottom:0;left:0;right:0;
  }
  path {
    stroke: black;
    stroke-width: 0.2;
    fill: none;
  }
  circle {
    fill: black;
    
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;svg id="svg" viewBox="-50 -50 100 100"&gt;
  &lt;g id="slice"&gt;
    &lt;path d="M8.390747629378028, 4.0407710911278985Q16.337096335644915,1.578047643071413 28.72564510652592,5.067456639486153Q41.114193877406926,8.556865635900893 22.230907302700192,4.260374440788638Q3.3476207279934576,-0.03611675432361651 21.46226478304126,-6.962030472005244Q39.57690883808906,-13.887944189686872 31.396381359458864,-2.1315394650039874Q23.215853880828664,9.624865259678897 22.336451060888443,2.1742972246208847Q21.457048240948225, -5.276270810437127, 8.390747629378028, -4.0407710911278985" id="theCurve"&gt;&lt;/path&gt;
    &lt;circle r="1"&gt;
    &lt;animateMotion begin="0s" dur="10s" repeatCount="indefinite"&gt;
      &lt;mpath xlink:href="#theCurve"&gt;&lt;/mpath&gt;  
    &lt;/animateMotion&gt;
    &lt;/circle&gt;
    &lt;/g&gt;
    
    &lt;use xlink:href="#slice" transform="rotate(200)"&gt;&lt;/use&gt;
    
  &lt;/svg&gt;</code></pre>
  </div>
  </div>
  </p>