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
fNullPreviewer.createControl(fPreviewContainer);
		fPreviewContainer.showPage(fNullPreviewer.getControl());
		fCurrentPreviewViewer= fNullPreviewer;
		fCurrentDescriptor= null;
		
		sashForm.setWeights(new int[]{33, 67});
		GridData gd= new GridData(GridData.FILL_BOTH);
		gd.widthHint= convertWidthInCharsToPixels(80);
		sashForm.setLayoutData(gd);
		Dialog.applyDialogFont(result);
		return result;
	}
	
	private Control createNullPage(Composite parent) {
		Composite result= new Composite(parent, SWT.NONE);
		GridLayout layout= new GridLayout();
		layout.marginWidth = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
		layout.marginHeight = convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
		result.setLayout(layout);
		Label label= new Label(result, SWT.CENTER);
		label.setText(RefactoringUIMessages.PreviewWizardPage_no_source_code_change); 
		label.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
		Dialog.applyDialogFont(result);
		return result;
	}
	
	/* (Non-JavaDoc)
	 * Method defined in IWizardPage
	 */
	public void setVisible(boolean visible) {