Bug 133375 [Viewers] Need access to the element comparer of a tree selection
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeSelection.java
/* Implementation note.  This class extends StructuredSelection because many pre-existing
	 * JFace viewer clients assumed that the only implementation of IStructuredSelection 
	 * was StructuredSelection.  By extending StructuredSelection rather than implementing
	 * ITreeSelection directly, we avoid this problem.
	 * For more details, see Bug 121939 [Viewers] TreeSelection should subclass StructuredSelection. 
	 */
	
	private TreePath[] paths = null;
	private CustomHashtable element2TreePaths = null;
	/**
	 * The canonical empty selection. This selection should be used instead of
	 * <code>null</code>.
	 */
	public static final TreeSelection EMPTY = new TreeSelection();
	
	private static final TreePath[] EMPTY_TREE_PATHS= new TreePath[0];
	
	private static class InitializeData {
		List selection;
		TreePath[] paths;
		CustomHashtable element2TreePaths;
		
		private InitializeData(TreePath[] paths, IElementComparer comparer) {