Bug 257855 [CommonNavigator] Supporting Custom Transfertypes in Common Navigator Framework
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonViewer.java
private final NavigatorContentService contentService;
	private ISelection cachedSelection;
	
	private FrameList frameList;
	
	private CommonNavigator commonNavigator;
	private ICommonViewerMapper _mapper;
	
	/**
	 * <p>
	 * Constructs the Tree Viewer for the Common Navigator and the corresponding
	 * NavigatorContentService. The NavigatorContentService will provide the
	 * Content Provider and Label Provider -- these need not be supplied by
	 * clients.
	 * <p>
	 * For the valid bits to supply in the style mask (aStyle), see
	 * documentation provided by {@link TreeViewer}.
	 * </p>
	 * 
	 * @param aViewerId
	 *            An id tied to the extensions that is used to focus specific
	 *            content to a particular instance of the Common Navigator
	 * @param aParent
	 *            A Composite parent to contain the actual SWT widget
	 * @param aStyle
	 *            A style mask that will be used to create the TreeViewer