Implementation class for {@link TreeItem}.

class TreeItemImpl {
 TreeItemImpl() {
   initializeClonableElements();
 }

 void convertToFullNode(TreeItem item) {
   if (item._imageHolder == null) {
     // Extract the Elements from the object
     dart_html.Element itemTable = Dom.clone(TreeItem._BASE_INTERNAL_ELEM, true);
     item.getElement().append(itemTable);
     dart_html.Element tr = Dom.getFirstChild(Dom.getFirstChild(itemTable));
     dart_html.Element tdImg = Dom.getFirstChild(tr);
     dart_html.Element tdContent = tdImg.nextElementSibling;

     // Undoes padding from table element.
     item.getElement().style.padding = "0px";
     tdContent.append(item._contentElem);
     item._imageHolder = tdImg;
   }
 }

 /**
  * Setup clonable elements.
  */
 void initializeClonableElements() {
   // Create the base table element that will be cloned.
   TreeItem._BASE_INTERNAL_ELEM = new dart_html.TableElement();
   dart_html.Element contentElem = new dart_html.DivElement();
   dart_html.Element tbody = (TreeItem._BASE_INTERNAL_ELEM as dart_html.TableElement).createTBody();
   dart_html.Element tr = new dart_html.TableRowElement();
   dart_html.Element tdImg = new dart_html.TableCellElement(), tdContent = new dart_html.TableCellElement();
   TreeItem._BASE_INTERNAL_ELEM.append(tbody);
   tbody.append(tr);
   tr.append(tdImg);
   tr.append(tdContent);
   tdImg.style.verticalAlign = "middle";
   tdContent.style.verticalAlign = "middle";
   tdContent.append(contentElem);
   contentElem.style.display = "inline";
   UiObject.setElementStyleName(contentElem, "dwt-TreeItem");
   TreeItem._BASE_INTERNAL_ELEM.style.whiteSpace = "nowrap";

   // Create the base element that will be cloned
   TreeItem._BASE_BARE_ELEM = new dart_html.DivElement();

   // Simulates padding from table element.
   TreeItem._BASE_BARE_ELEM.style.padding = "3px";
   TreeItem._BASE_BARE_ELEM.append(contentElem);
//    Roles.getTreeitemRole().set(contentElem);
 }
}