Bug 315281 update copyrights for 3.6
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonViewerSorter.java
* @see org.eclipse.jface.viewers.ViewerSorter#category(java.lang.Object)
	 */
	public int category(Object element) {
		if (contentService == null)
			return 0;
		INavigatorContentDescriptor source = getSource(element);
		return source != null ? source.getSequenceNumber() : Priority.NORMAL_PRIORITY_VALUE;
	}
	private void logMissingExtension(Object parent, Object object) {
		NavigatorPlugin.logError(0, NLS.bind(CommonNavigatorMessages.CommonViewerSorter_NoContentExtensionForObject,
				object != null ? object.toString() : "<null>", parent != null ? parent.toString() : "<null>"), null); 
	}
	
	public int compare(Viewer viewer, TreePath parentPath, Object e1, Object e2) {
		if (contentService == null)
			return -1;
		INavigatorContentDescriptor sourceOfLvalue = getSource(e1);
		INavigatorContentDescriptor sourceOfRvalue = getSource(e2);
		
		Object parent;
		if (parentPath == null) {
			parent = viewer.getInput();
		} else {
			parent = parentPath.getLastSegment();
		}
		
		if (sourceOfLvalue == null) {
			logMissingExtension(parent, e1);
			return -1;
		}