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
});
		}
	}
	/**
	 * Fires a tree expanded event. Only listeners registered at the time this
	 * method is called are notified.
	 * 
	 * @param event
	 *            the tree expansion event
	 * @see ITreeViewerListener#treeExpanded
	 */
	protected void fireTreeExpanded(final TreeExpansionEvent event) {
		Object[] listeners = treeListeners.getListeners();
		for (int i = 0; i < listeners.length; ++i) {
			final ITreeViewerListener l = (ITreeViewerListener) listeners[i];
			SafeRunnable.run(new SafeRunnable() {
				public void run() {
					l.treeExpanded(event);
				}
			});
		}
	}
	/**
	 * 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() {