code: function getMenuSize(tab) {
  	    var clone = tab.cloneNode(true);
  	    clone.style.position = 'absolute';
  	    clone.style.opacity = 0;
  	    clone.removeAttribute('hidden'); // Append to parent so we get the "real" size
  
  	    tab.parentNode.appendChild(clone); // Get the sizes before we remove
  
  	    var width = clone.scrollWidth;
  	    var height = clone.scrollHeight; // Remove from the DOM
  
  	    removeElement(clone);
  	    return {
  	      width: width,
  	      height: height
  	    };
  	  }
docs: Get the natural size of a menu panel