Bug 93400 LTK UI should provide official API for structural content in the preview page
org.eclipse.ltk.ui.refactoring/src/org/eclipse/ltk/internal/ui/refactoring/PseudoLanguageChangeElement.java
private List fChildren;
	private GroupCategorySet fGroupCategories;
	
	public PseudoLanguageChangeElement(ChangeElement parent) {
		super(parent);
	}
	public Change getChange() {
		return null;
	}
	
	public ChangePreviewViewerDescriptor getChangePreviewViewerDescriptor() throws CoreException {
		DefaultChangeElement element= getDefaultChangeElement();
		if (element == null)
			return null;
		return element.getChangePreviewViewerDescriptor();
	}
	
	public void feedInput(IChangePreviewViewer viewer, List categories) throws CoreException {
		DefaultChangeElement element= getDefaultChangeElement();
		if (element != null) {
			Change change= element.getChange();
			if (change instanceof TextEditBasedChange) {
				List groups= collectTextEditBasedChangeGroups(categories);
				viewer.setInput(TextEditChangePreviewViewer.createInput(change,
					(TextEditBasedChangeGroup[])groups.toArray(new TextEditBasedChangeGroup[groups.size()]),
					getTextRange()));
			}
		} else {