Bug 38782 TreeViewer add calls a refresh
Our implementation of TreeViewer.add is naive and can all a refresh of the entire tree. It should be more like TableViewer.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* the given element.
	 *
	 * @param parent the parent widget
	 * @param element the element
	 * @param index if non-negative, indicates the position to insert the item 
	 *    into its parent
	 */
	protected void createTreeItem(Widget parent, Object element, int index) {
		Item item = newItem(parent, SWT.NULL, index);
		updateItem(item, element);
		updatePlus(item, element);
	}
	/**
	 * The <code>AbstractTreeViewer</code> implementation of this method
	 * also recurses over children of the corresponding element.
	 */
	protected void disassociate(Item item) {
		super.disassociate(item);
		
		
		
		if (usingElementMap())
			disassociateChildren(item);
	}
	/**
	 * Disassociates the children of the given SWT item from their
	 * corresponding elements.
	 *
	 * @param item the widget
	 */