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
/** 
	 * Constant indicating that all levels of the tree should be expanded or collapsed.
	 *
	 * @see #expandToLevel
	 * @see #collapseToLevel
	 */
	public static final int ALL_LEVELS = -1;
	/**
	 * List of registered tree listeners (element type: <code>TreeListener</code>).
	 */
	private ListenerList treeListeners = new ListenerList(1);
	/**
	 * The level to which the tree is automatically expanded each time
	 * the viewer's input is changed (that is, by <code>setInput</code>).
	 * A value of 0 means that auto-expand is off.
	 *
	 * @see #setAutoExpandLevel
	 */
	private int expandToLevel = 0;
	/**
	 * The safe runnable used to call the label provider.
	 */
	private UpdateItemSafeRunnable safeUpdateItem =
		new UpdateItemSafeRunnable();
	class UpdateItemSafeRunnable extends SafeRunnable {