Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentExtension.java
*            The content service that will manage this extension
	 * @param aViewerManager
	 *            The viewer manager that knows how to initialize the content
	 *            provider created by this extension.
	 */
	public NavigatorContentExtension(NavigatorContentDescriptor aDescriptor,
			NavigatorContentService aContentService,
			StructuredViewerManager aViewerManager) {
		super();
		Assert.isNotNull(aDescriptor);
		descriptor = aDescriptor;
		contentService = aContentService;
		viewerId = contentService.getViewerId();
		viewerManager = aViewerManager;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentExtension#getId()
	 */
	public String getId() {
		return descriptor.getId();
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentExtension#getDescriptor()
	 */
	public INavigatorContentDescriptor getDescriptor() {
		return descriptor;