Bug 144294 Performance: CommonNavigator could easily cache its ISelection to improve its performance
Currently, the CommonNavigator does not override the getSelection() method, which is quite expensive when called repeatedly by clients since it gets the current selection from the underlying SWT widget each time it gets called. A simple trick is to cache the selection and update it only when it actually changes. This would result in improved performance for clients who call getSelection() often. This defect is related to 140032. Please refer to it for more info. I will be submitting a patch shortly.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonViewer.java
* </p>
	 */
	public void dispose() {
		if (contentService != null) {
			contentService.dispose();
		}
	}
	/**
	 * Sets this viewer's sorter and triggers refiltering and resorting of this
	 * viewer's element. Passing <code>null</code> turns sorting off.
	 * 
	 * @param sorter
	 *            a viewer sorter, or <code>null</code> if none
	 */
	public void setSorter(ViewerSorter sorter) {
		if (sorter != null && sorter instanceof CommonViewerSorter) {
			((CommonViewerSorter) sorter).setContentService(contentService);
		}
		super.setSorter(sorter);
	}
	/**
	 * <p>
	 * The {@link INavigatorContentService}provides the hook into the framework
	 * to provide content from the various extensions.
	 * </p>
	 * 
	 * @return The {@link INavigatorContentService}that was created when the
	 *         viewer was created.
	 */
	public INavigatorContentService getNavigatorContentService() {