Find the `top` of an item relative to the content element, and also the height.
function refreshPosition(item) {
      // Find the top of an item by adding to the offsetHeight until we reach the 
      // content element.
      var current = item.element[0];
      item.top = 0;
      item.left = 0;
      item.right = 0;
      while (current && current !== contentEl[0]) {
        item.top += current.offsetTop;
        item.left += current.offsetLeft;
        if ( current.offsetParent ){
          item.right += current.offsetParent.offsetWidth - current.offsetWidth - current.offsetLeft; //Compute offsetRight
        }
        current = current.offsetParent;
      }
      item.height = item.element.prop('offsetHeight');

      var defaultVal = $mdUtil.floatingScrollbars() ? '0' : undefined;
      $mdUtil.bidi(item.clone, 'margin-left', item.left, defaultVal);
      $mdUtil.bidi(item.clone, 'margin-right', defaultVal, item.right);
    }