Bug 161086 [Viewers] performance problem in AbstractTreeViewer.internalExpandToLevel
If you expand to ALL_LEVELS, internalExpandToLevel will call createChildren even if the element has no children, i.e. it does not check if the element is expandable. Found this while experimenting with the Quick Access feature (enter "con", then delete all three characters one at a time).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
}
				}
			}
			if (newItem) {
				createTreeItem(widget, element, index);
			}
		}
	}
	/**
	 * See if element is the data of one of the elements in items.
	 * 
	 * @param items
	 * @param element
	 * @return <code>true</code> if the element matches.
	 */
	private boolean itemExists(Item[] items, Object element) {
		if (usingElementMap()) {
			Widget[] existingItems = findItems(element);
			
			if (existingItems.length == 0) {
				return false;
			} else if (existingItems.length == 1) {
				if (items.length > 0 && existingItems[0] instanceof Item) {
					Item existingItem = (Item) existingItems[0];
					return getParentItem(existingItem) == getParentItem(items[0]);
				}
			}
		}
		for (int i = 0; i < items.length; i++) {
			if (items[i].getData().equals(element)) {