// Begins Undo Unit
public UndoUnit(HTMLDocument document, string title)
{
markupServices = document as IMarkupServicesRaw;
markupServices.BeginUndoUnit(title);
}
/// <summary>
/// Marks the beginning of a reversible unit of work.
/// </summary>
/// <param name="title">the title of a reversible unit of work</param>
public void BeginUndoUnit(string title)
{
MarkupServices.BeginUndoUnit(title);
}