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
* <p>
	 * This method should be called (by the content provider) when a single element 
	 * has been added to the model, in order to cause the viewer to accurately
	 * reflect the model. This method only affects the viewer, not the model.
	 * Note that there is another method for efficiently processing the simultaneous
	 * addition of multiple elements.
	 * </p>
	 *
	 * @param parentElement the parent element
	 * @param childElement the child element
	 */
	public void add(Object parentElement, Object childElement) {
		add(parentElement, new Object[] { childElement });
	}
	/**
	 * Adds the given SWT selection listener to the given SWT control.
	 *
	 * @param control the SWT control
	 * @param listener the SWT selection listener
	 * 
	 * @deprecated
	 */
	protected void addSelectionListener(
		Control control,
		SelectionListener listener) {
	}
	/**
	 * Adds a listener for expand and collapse events in this viewer.
	 * Has no effect if an identical listener is already registered.
	 *