code: function render() {
        var checked = rgCtrl.getViewValue() == attr.value;
  
        if (checked === lastChecked) return;
  
        if (element[0].parentNode.nodeName.toLowerCase() !== 'md-radio-group') {
          // If the radioButton is inside a div, then add class so highlighting will work
          element.parent().toggleClass(CHECKED_CSS, checked);
        }
  
        if (checked) {
          rgCtrl.setActiveDescendant(element.attr('id'));
        }
  
        lastChecked = checked;
  
        element
          .attr('aria-checked', checked)
          .toggleClass(CHECKED_CSS, checked);
      }
docs: Add or remove the `.md-checked` class from the RadioButton (and conditionally its parent).
  Update the `aria-activedescendant` attribute.