Bug 156883 [Viewers] enhancements to ILazyTreeContentProvider
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
} else {
				if (widget instanceof Tree) {
					((Tree) widget).setItemCount(0);
				} else {
					((TreeItem) widget).setItemCount(0);
				}
			}
			
			
			Item[] items = getChildren(widget);
			for (int i = 0; i < items.length; i++) {
				Item item = items[i];
				Object data = item.getData();
				if (data != null) {
					virtualRefreshChildCounts(item, data);
				}
			}
		}
	}
	/*
	 * To unmap elements correctly, we need to register a dispose listener with
	 * the item if the tree is virtual.
	 */
	protected void mapElement(Object element, final Widget item) {
		super.mapElement(element, item);
		
		if ((getTree().getStyle() & SWT.VIRTUAL) != 0) {
			
			
			if (item.getData(VIRTUAL_DISPOSE_KEY) == null) {