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/PreviewWizardPage.java
public PreviousChange() {
			setImageDescriptor(CompareUI.DESC_ETOOL_PREV);
			setDisabledImageDescriptor(CompareUI.DESC_DTOOL_PREV);
			setHoverImageDescriptor(CompareUI.DESC_CTOOL_PREV);
			setToolTipText(RefactoringUIMessages.PreviewWizardPage_previous_Change); 
			PlatformUI.getWorkbench().getHelpSystem().setHelp(this, IRefactoringHelpContextIds.PREVIOUS_CHANGE_ACTION);			
		}	
		public void run() {
			fTreeViewer.revealPrevious();
		}
	}
	
	private class FilterAction extends Action {
		private FilterDropDownAction fOwner;
		private GroupCategory fGroupCategory;
		public FilterAction(FilterDropDownAction owner, GroupCategory category) {
			super(category.getName(), IAction.AS_RADIO_BUTTON);
			setToolTipText(category.getDescription());
			fOwner= owner;
			fGroupCategory= category;
		}
		public void run() {
			setActiveGroupCategory(fGroupCategory);
			fOwner.executed(this);
		}
	}
	private class ShowAllAction extends Action {