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
}
	/**
	 * This implementation of getSelection() returns an instance of
	 * ITreeSelection.
	 * 
	 * @since 3.2
	 */
	public ISelection getSelection() {
		Control control = getControl();
		if (control == null || control.isDisposed()) {
			return TreeSelection.EMPTY;
		}
		Widget[] items = getSelection(getControl());
		ArrayList list = new ArrayList(items.length);
		for (int i = 0; i < items.length; i++) {
			Widget item = items[i];
			if (item.getData() != null) {
				list.add(getTreePathFromItem((Item) item));
			}
		}
		return new TreeSelection((TreePath[]) list.toArray(new TreePath[list
				.size()]), getComparer());
	}
	protected void setSelectionToWidget(ISelection selection, boolean reveal) {
		if (selection instanceof ITreeSelection) {
			ITreeSelection treeSelection = (ITreeSelection) selection;
			setSelectionToWidget(Arrays.asList(treeSelection.getPaths()),
					reveal);
		} else {
			super.setSelectionToWidget(selection, reveal);