function postLink(scope, element, attrs) {
      // backdrop may be outside the $rootElement, tell ngAnimate to animate regardless
      if ($animate.pin) $animate.pin(element, $rootElement);

      var bodyStyles;

      $$rAF(function() {
        // If body scrolling has been disabled using mdUtil.disableBodyScroll(),
        // adjust the 'backdrop' height to account for the fixed 'body' top offset.
        // Note that this can be pretty expensive and is better done inside the $$rAF.
        bodyStyles = $window.getComputedStyle($document[0].body);

        if (bodyStyles.position === 'fixed') {
          var resizeHandler = $mdUtil.debounce(function(){
            bodyStyles = $window.getComputedStyle($document[0].body);
            resize();
          }, 60, null, false);

          resize();
          angular.element($window).on('resize', resizeHandler);

          scope.$on('$destroy', function() {
            angular.element($window).off('resize', resizeHandler);
          });
        }

        // Often $animate.enter() is used to append the backDrop element
        // so let's wait until $animate is done...
        var parent = element.parent();

        if (parent.length) {
          if (parent[0].nodeName === 'BODY') {
            element.css('position', 'fixed');
          }

          var styles = $window.getComputedStyle(parent[0]);

          if (styles.position === 'static') {
            // backdrop uses position:absolute and will not work properly with parent position:static (default)
            $log.warn(ERROR_CSS_POSITION);
          }

          // Only inherit the parent if the backdrop has a parent.
          $mdTheming.inherit(element, parent);
        }
      });

      function resize() {
        var viewportHeight = parseInt(bodyStyles.height, 10) + Math.abs(parseInt(bodyStyles.top, 10));
        element.css('height', viewportHeight + 'px');
      }
    }
@ngdoc directive
@name mdBackdrop
@module material.components.backdrop

@restrict E

@description
`<md-backdrop>` is a backdrop element used by other components, such as dialog and bottom sheet.
Apply class `opaque` to make the backdrop use the theme backdrop color.