Bug 139511 [CommonNavigator] getParent() fails in certain cases
In the implementation of getParents(), clients can sometimes fail to return the correct parent with the override cases taken into account. The attached patch fixes these issues, but should be reviewed by the Team Team to ensure that it does not cause any regressions for their cases.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptorManager.java
* 
	 * Returns all content descriptor(s) which enable for the given element.
	 * 
	 * @param anElement
	 *            the element to return the best content descriptor for
	 * 
	 * @param aVisibilityAssistant
	 *            The relevant viewer assistant; used to filter out unbound
	 *            content descriptors.
	 * @return the best content descriptor for the given element.
	 */
	public Set findDescriptorsForPossibleChild(Object anElement,
			VisibilityAssistant aVisibilityAssistant) {
		return findDescriptorsForPossibleChild(anElement, aVisibilityAssistant, true);
	}
	/**
	 * 
	 * Returns all content descriptor(s) which enable for the given element.
	 * 
	 * @param anElement
	 *            the element to return the best content descriptor for
	 * 
	 * @param aVisibilityAssistant
	 *            The relevant viewer assistant; used to filter out unbound
	 *            content descriptors.
	 * @return the best content descriptor for the given element.
	 */
	public Set findDescriptorsForPossibleChild(Object anElement,
			VisibilityAssistant aVisibilityAssistant, boolean toComputeOverrides) {
		EvaluationCache cache = getEvaluationCache(