Bug 305739 [viewers] #expandToLevel(Object, level) retrieves all children when virtual
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
private Object element;
		private Item item;
		UpdateItemSafeRunnable(Item item, Object element) {
			this.item = item;
			this.element = element;
		}
		public void run() {
			doUpdateItem(item, element);
		}
	}