Bug 275910 [Widgets] PaintListener on Tree not invoked when item count is 0
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/ExtendedMarkersView.java
* @param contentGeneratorId
	 *            the id of the generator to load.
	 */
	public ExtendedMarkersView(String contentGeneratorId) {
		super();
		defaultGeneratorIds = new String[] { contentGeneratorId };
	}
	/**
	 * Create a preference listener for any preference updates.
	 */ 
	
	
	/**
	 * Add all concrete {@link MarkerSupportItem} elements associated with the
	 * receiver to allMarkers.
	 * 
	 * @param markerItem
	 * @param allMarkers
	 */
	private void addAllConcreteItems(MarkerSupportItem markerItem,
			Collection allMarkers) {
		if (markerItem.isConcrete()) {
			allMarkers.add(markerItem);
			return;
		}
		MarkerSupportItem[] children = markerItem.getChildren();
		for (int i = 0; i < children.length; i++) {
			addAllConcreteItems(children[i], allMarkers);
		}
	}