Bug 239015 [Databinding] ObservableListTreeContentProvider adds the value passed to TreeViewer#setInput() to the known-elements
The input element is never shown in the viewer so it should no get part of the knownElements further more it restricts the usability of the content-provider because the input-element itself already has to provide the required Observable-Attribute(s).
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/viewers/ObservableCollectionTreeContentProvider.java
ITreeContentProvider {
	private Realm realm;
	private IObservableValue viewerObservable;
	/**
	 * Interfaces for sending updates to the viewer.
	 */
	protected TreeViewerUpdater viewerUpdater;
	/**
	 * Element comparer used by the viewer (may be null).
	 */
	protected IElementComparer comparer;
	private IObservableSet knownElements;
	private IObservableSet unmodifiableKnownElements;
	private IObservableFactory collectionFactory;
	private Map elementNodes;
	private TreeStructureAdvisor structureAdvisor;
	/**
	 * Constructs an ObservableCollectionTreeContentProvider using the given
	 * parent provider and collection factory.
	 * 
	 * @param collectionFactory
	 *            observable factory that produces an IObservableList of
	 *            children for a given parent element.
	 * @param structureAdvisor
	 */
	protected ObservableCollectionTreeContentProvider(