code: function(root) {
  
              root = root || this.innerElement;
  
              var focusable = {};
              for (var i = 0; i < Panel.FOCUSABLE.length; i++) {
                  focusable[Panel.FOCUSABLE[i]] = true;
              }
  
              function isFocusable(el) {
                  if (el.focus && el.type !== "hidden" && !el.disabled && focusable[el.tagName.toLowerCase()]) {
                      return true;
                  }
                  return false;
              }
  
              // Not looking by Tag, since we want elements in DOM order
              return Dom.getElementsBy(isFocusable, null, root);
          }
docs: Returns an array of the currently focusable items which reside within
  Panel. The set of focusable elements the method looks for are defined
  in the Panel.FOCUSABLE static property
  
  @method getFocusableElements
  @param {HTMLElement} root element to start from.