anchor.diff:  }
   
   class TextFormatter extends CellFormatter {
  -  bool handleRequest(Event e) {
  +  bool _handleRequest(Event e) {
       var input = e.target;
       input.style.textAlign = 'left';
       return true;
  
positive.code: 
    void processRequest(Event e) {
      if (!isCell(e)) return;
      if (handleRequest(e)) return;
      if (nextHandler == null) return;
  
      nextHandler.processRequest(e);
    }
  
    bool handleRequest(Event e) => false;
  
    bool isCell(Event e) {
      var input = e.target;
  
negative.code: }
  
  class DateFormatter extends CellFormatter {
    bool _handleRequest(Event e) {
      var input = e.target;
      RegExp exp = new RegExp(r"^\s*[\d/-]+\s*$");
      if (!exp.hasMatch(input.value)) return false;
  