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
findOverridingLabelExtensions(anElement, ncd, contributors);
		}
		return contributors;
	}
	private void findOverridingLabelExtensions(Object anElement,
			INavigatorContentDescriptor descriptor, LinkedHashSet contributors) {
		ListIterator iter = ((NavigatorContentDescriptor) descriptor).getOverridingExtensionsListIterator(false);
		while (iter.hasPrevious()) {
			INavigatorContentDescriptor child = (INavigatorContentDescriptor) iter.previous();
			if (assistant.isVisibleAndActive(child) && child.isPossibleChild(anElement)) {
				findOverridingLabelExtensions(anElement, child, contributors);
			}
		}
		contributors.add(getExtension(descriptor));
	}
	
	/**
	 * 
	 * The label provider that is are enabled for the given element.
	 * A label provider is 'enabled' if its corresponding content provider
	 * returned the element.
	 * 
	 * @param anElement
	 *            An element from the tree (any element contributed to the
	 *            tree).
	 * @return The label provider
	 */
	public ILabelProvider[] findRelevantLabelProviders(Object anElement) {
		Collection extensions = findPossibleLabelExtensions(anElement);