Bug 126839 [DataBinding] IObservable refactoring
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/viewers/TreeViewerUpdatableTreeExtended.java
}
			public String isValid(Object value) {
				return null;
			}
		});		
	}
	
	protected CellEditor createCellEditor(final Column column) {
		return new TextCellEditor(treeViewerDescription.getTreeViewer().getTree()) {				
			protected void doSetValue(Object value) {
				super.doSetValue( column.getConverter().convertModelToTarget(value));
			}
			protected Object doGetValue() {
				String textValue = (String)super.doGetValue();
				return column.getConverter().convertTargetToModel(textValue);
			}
		};
		
	}
	private void fillDescriptionDefaults(final IDataBindingContext dataBindingContext) {
		Class[] types = treeViewerDescription.getClassTypes();
		if (types==null) {
			return;
		}
		
		for (int i=0; i<types.length; i++) {
			int colCount = treeViewerDescription.getColumnCount(types[i]);					
			for (int j = 0; j < colCount; j++) {
				Column column = treeViewerDescription.getColumn(types[i], j);
				ColumnInfo info = new ColumnInfo();