contents.add(new BookmarkableFolderContent(tree));
contents.add(new LabelContent());
contents.add(new MultiLineLabelContent());
contents.add(new FolderContent());
contents.add(new EditableFolderContent());
contents.add(new SelectableFolderContent(provider));
contents.add(new MultiSelectableFolderContent(provider));
contents.add(new CheckedFolderContent(provider));
contents.add(new CheckedSelectableFolderContent(provider));
contents.add(new PanelContent());