code: function fixKeyframes(rootElement) {
      const animationNameProp = [
          'animation-name',
          '-moz-animation-name',
          '-webkit-animation-name'
      ].filter(prop => getComputedStyle(document.body)[prop])[0];
  
      if (animationNameProp) {
          const allNodes      = rootElement.getElementsByTagName('*');
          const keyframeNodes = [];
          const nameMarker    = '__CSSVARSPONYFILL-KEYFRAMES__';
  
          // Modify animation name
          for (let i = 0, len = allNodes.length; i < len; i++) {
              const node          = allNodes[i];
              const animationName = getComputedStyle(node)[animationNameProp];
  
              if (animationName !== 'none') {
                  node.style[animationNameProp] += nameMarker;
                  keyframeNodes.push(node);
              }
          }
  
          // Force reflow
          void document.body.offsetHeight;
  
          // Restore animation name
          for (let i = 0, len = keyframeNodes.length; i < len; i++) {
              const nodeStyle = keyframeNodes[i].style;
  
              nodeStyle[animationNameProp] = nodeStyle[animationNameProp].replace(nameMarker, '');
          }
      }
  }
docs: Fixes issue with keyframe properties set using CSS custom property not being
  applied properly in some legacy (IE) and modern (Safari) browsers.
  
  @param {object} rootElement