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
fActiveAction.setChecked(false);
			fActiveAction= action;
			fActiveAction.setChecked(true);
		}
	}
	
	private Change fChange;
	private List fActiveGroupCategories;
	private CompositeChange fTreeViewerInputChange;
	private ChangeElement fCurrentSelection;
	private PageBook fPageContainer;
	private Control fStandardPage;
	private Control fNullPage;
	private FilterDropDownAction fFilterDropDownAction;
	private ViewerPane fTreeViewerPane;
	private ChangeElementTreeViewer fTreeViewer;
	private PageBook fPreviewContainer;
	private ChangePreviewViewerDescriptor fCurrentDescriptor;
	private IChangePreviewViewer fCurrentPreviewViewer;
	private IChangePreviewViewer fNullPreviewer;
	
	/**
	 * Creates a new proposed changes wizard page.
	 */
	public PreviewWizardPage() {
		super(PAGE_NAME);
		setDescription(RefactoringUIMessages.PreviewWizardPage_description); 
	}
	/**
	 * Sets the given change. Setting the change initializes the tree viewer with