Bug 287621 [CommonNavigator] Add more tracing
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
IMementoAware, INavigatorContentService {
	/**
	 * 
	 */
	public static final String WIDGET_KEY = "org.eclipse.ui.navigator"; 
	
	private static final NavigatorContentDescriptorManager CONTENT_DESCRIPTOR_REGISTRY = NavigatorContentDescriptorManager
			.getInstance();
	private static final NavigatorViewerDescriptorManager VIEWER_DESCRIPTOR_REGISTRY = NavigatorViewerDescriptorManager
			.getInstance();
	private static final ITreeContentProvider[] NO_CONTENT_PROVIDERS = new ITreeContentProvider[0];
	private static final ILabelProvider[] NO_LABEL_PROVIDERS = new ILabelProvider[0];
	private static final INavigatorContentDescriptor[] NO_DESCRIPTORS = new INavigatorContentDescriptor[0];
	private static final String[] NO_EXTENSION_IDS = new String[0];
	private final NavigatorViewerDescriptor viewerDescriptor;
	private final List listeners = new ArrayList();
	/*
	 * A map of (String-based-Navigator-Content-Extension-IDs,
	 * NavigatorContentExtension-objects)-pairs
	 */