Bug 305739 [viewers] #expandToLevel(Object, level) retrieves all children when virtual
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
* object or an empty tree path.
	 *
	 * @param elementOrTreePath
	 *            the element, or tree path
	 * @param count
	 *
	 * @since 3.2
	 */
	public void setChildCount(final Object elementOrTreePath, final int count) {
		if (checkBusy())
			return;
		preservingSelection(new Runnable() {
			public void run() {
				if (internalIsInputOrEmptyPath(elementOrTreePath)) {
					getTree().setItemCount(count);
					return;
				}
				Widget[] items = internalFindItems(elementOrTreePath);
				for (int i = 0; i < items.length; i++) {
					TreeItem treeItem = (TreeItem) items[i];
					treeItem.setItemCount(count);
				}
			}
		});
	}
	/**
	 * For a TreeViewer with a tree with the VIRTUAL style bit set, replace the
	 * given parent's child at index with the given element. If the given parent
	 * is this viewer's input or an empty tree path, this will replace the root
	 * element at the given index.