Bug 287103 [CommonNavigator] contentServiceLabelProvider doesn't properly implement overrides
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptor.java
} else if (enablement != null) {
				return (enablement.evaluate(context) == EvaluationResult.TRUE);
			}
		} catch (CoreException e) {
			NavigatorPlugin.logError(0, e.getMessage(), e);
		}
		return false;
	}
	
	/**
	 * A convenience method to check all elements in a selection. 
	 * 
	 * @param aSelection A non-null selection
	 * @return True if and only if every element in the selection is a possible child.
	 */
	public boolean arePossibleChildren(IStructuredSelection aSelection) {
		if(aSelection.isEmpty()) {
			return false;
		}
		for (Iterator iter = aSelection.iterator(); iter.hasNext();) {
			Object element = iter.next();
			if(!isPossibleChild(element)) {
				return false;
			}			
		}
		return true;
	}
	/**
	 * 
	 * Does not force the creation of the set of overriding extensions.