Bug 305739 [viewers] #expandToLevel(Object, level) retrieves all children when virtual
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
if (isSameSelection(items, current)) {
			return;
		}
		TreeItem[] newItems = new TreeItem[items.size()];
		items.toArray(newItems);
		getTree().setSelection(newItems);
	}
	/*
	 * (non-Javadoc) Method declared in AbstractTreeViewer.
	 */
	protected void showItem(Item item) {
		getTree().showItem((TreeItem) item);
	}
	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jface.viewers.AbstractTreeViewer#getChild(org.eclipse.swt.widgets.Widget,
	 *      int)
	 */
	protected Item getChild(Widget widget, int index) {
		if (widget instanceof TreeItem) {
			return ((TreeItem) widget).getItem(index);
		}
		if (widget instanceof Tree) {
			return ((Tree) widget).getItem(index);
		}
		return null;
	}
	protected void assertContentProviderType(IContentProvider provider) {