Bug 156883 [Viewers] enhancements to ILazyTreeContentProvider
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() {
		return expandToLevel;
	}
	/**
	 * Returns the SWT child items for the given SWT widget.