anchor.diff:   *
    * API is not finalized yet, do not use.
    */
  -class XmlBuilder {
  +class XmlBuilder implements XmlWritable {
   
     final List<_XmlNodeBuilder> _stack = new List.from([new _XmlDocumentBuilder()]);
   
  
positive.code:    */
    XmlNode build() => _stack.last.build();
  
    @override
    String toString() => build().toString();
  
    // Internal method to build a name.
    XmlName _buildName(String name, String uri) {
      return uri == null || uri.isEmpty
  
negative.code:     }
    }
  
    @override
    void writeTo(StringBuffer buffer) {
      build().writeTo(buffer);
    }
  
    @override
    void writePrettyTo(StringBuffer buffer, int level, String indent) {
      build().writePrettyTo(buffer, level, indent);
    }
  
  }
  
  abstract class _XmlNodeBuilder {
  