Bug 299438 [CommonNavigator] CNF viewer state non properly reset when NCEs are activated or deactivated
The map of the objects to the NCEs should be reset whenever the NCEs associated with the viewer to change to avoid having stale label information. This has shown up when looking at the CNF tests that change the viewer.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
/*
		 * If the descriptor instance hasn't been created yet, then we need to
		 * (1) verify that it wasn't added by another thread, (2) create and add
		 * the result into the map
		 */
		synchronized (this) {
			extension = (NavigatorContentExtension) contentExtensions
					.get(aDescriptorKey);
			if (extension == null) {
				contentExtensions.put(aDescriptorKey,
						(extension = new NavigatorContentExtension(
								(NavigatorContentDescriptor) aDescriptorKey,
								this, structuredViewerManager)));
				notifyListeners(extension);
			}
		}
		return extension;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @seeorg.eclipse.ui.internal.navigator.INavigatorContentService#
	 * getViewerDescriptor()
	 */
	public INavigatorViewerDescriptor getViewerDescriptor() {
		return viewerDescriptor;
	}
	/*
	 * (non-Javadoc)
	 *