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
Composite result= new Composite(parent, SWT.NONE);
		GridLayout layout= new GridLayout();
		layout.marginHeight= 0; layout.marginWidth= 0;
		result.setLayout(layout);
		
		SashForm sashForm= new SashForm(result, SWT.VERTICAL);
		
		fTreeViewerPane= new ViewerPane(sashForm, SWT.BORDER | SWT.FLAT);
		fTreeViewerPane.setText(RefactoringUIMessages.PreviewWizardPage_changes); 
		ToolBarManager tbm= fTreeViewerPane.getToolBarManager();
		tbm.add(new NextChange());
		tbm.add(new PreviousChange());
		tbm.add(new Separator());
		fFilterDropDownAction= new FilterDropDownAction();
		fFilterDropDownAction.setEnabled(false);
		tbm.add(fFilterDropDownAction);
		
		tbm.update(true);
		
		fTreeViewer= createTreeViewer(fTreeViewerPane);
		fTreeViewer.setContentProvider(createTreeContentProvider());
		fTreeViewer.setLabelProvider(createTreeLabelProvider());
		fTreeViewer.addSelectionChangedListener(createSelectionChangedListener());
		fTreeViewer.addCheckStateListener(createCheckStateListener());
		fTreeViewerPane.setContent(fTreeViewer.getControl());
		setTreeViewerInput();
		
		fPreviewContainer= new PageBook(sashForm, SWT.NONE);
		fNullPreviewer= new NullPreviewer();