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
* the given change.
	 * @param change the new change.
	 */
	public void setChange(Change change) {
		if (fChange == change)
			return;
		
		fChange= change;
		if (fChange instanceof CompositeChange) {
			fTreeViewerInputChange= (CompositeChange)fChange;
		} else {
			fTreeViewerInputChange= new CompositeChange("Dummy Change"); 
			fTreeViewerInputChange.add(fChange);
		}
		setTreeViewerInput();
	}
	/**
	 * Creates the tree viewer to present the hierarchy of changes. Subclasses may override
	 * to create their own custom tree viewer.
	 * 
	 * @param parent the tree viewer's parent
	 * 
	 * @return the tree viewer to present the hierarchy of changes
	 */
	protected ChangeElementTreeViewer createTreeViewer(Composite parent) {
		return new ChangeElementTreeViewer(parent);
	}
	
	/**
	 * Creates the content provider used to fill the tree of changes. Subclasses may override