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
}
	/**
	 * Returns the auto-expand level.
	 *
	 * @return non-negative level, or <code>ALL_LEVELS</code> if
	 *  all levels of the tree are expanded automatically
	 * @see #setAutoExpandLevel
	 */
	public int getAutoExpandLevel() {
		return expandToLevel;
	}
	/**
	 * Returns the SWT child items for the given SWT widget.
	 *
	 * @param widget the widget
	 * @return the child items
	 */
	protected abstract Item[] getChildren(Widget widget);
	/**
	 * Returns whether the given SWT item is expanded or collapsed.
	 *
	 * @param item the item
	 * @return <code>true</code> if the item is considered expanded
	 * and <code>false</code> if collapsed
	 */
	protected abstract boolean getExpanded(Item item);
	/**
	 * Returns a list of elements corresponding to expanded nodes in this
	 * viewer's tree, including currently hidden ones that are marked as
	 * expanded but are under a collapsed ancestor.