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.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* <li>discovers the old selection (via <code>getSelection</code>)</li>
	 * <li>runs the given runnable</li>
	 * <li>attempts to restore the old selection (using
	 * <code>setSelectionToWidget</code></li>
	 * <li>rediscovers the resulting selection (via <code>getSelection</code>)</li>
	 * <li>calls <code>handleInvalidSelection</code> if the resulting selection
	 * is different from the old selection</li>
	 * </ul>
	 * </p>
	 * 
	 * @param updateCode
	 *            the code to run
	 * 
	 * see #getPreserveSelection()
	 */
	protected void preservingSelection(Runnable updateCode) {
		preservingSelection(updateCode, false);
	}
	/**
	 * Attempts to preserves the current selection across a run of the given
	 * code, with a best effort to avoid scrolling if <code>reveal</code> is
	 * false, or to reveal the selection if <code>reveal</code> is true.
	 * <p>
	 * The default implementation of this method:
	 * <ul>
	 * <li>discovers the old selection (via <code>getSelection</code>)</li>
	 * <li>runs the given runnable</li>
	 * <li>attempts to restore the old selection (using
	 * <code>setSelectionToWidget</code></li>
	 * <li>rediscovers the resulting selection (via <code>getSelection</code>)</li>