anchor.diff:  /// displayed to the user, but the console is untouched if the compilation
   /// finished quickly.  The purpose is to reduce flicker in the UI.
   const Duration SLOW_COMPILE = const Duration(seconds: 1);
  +
  +const int TAB_WIDTH = 2;
   
   /**
    * UI interaction manager for the entire application.
  
positive.code:                 ..error('Unexpected node')
                  ..dir(node);
            }
          }
          break;
        }
  
negative.code:   }
  
    void onModifiedKeyUp(KeyboardEvent event) {
      if (event.getModifierState("Shift")) return onShiftedKeyUp(event);
      switch (event.keyCode) {
        case KeyCode.S:
          // Disable Ctrl-S, Cmd-S, etc. We have observed users hitting these
          // keys often when using Try Dart and getting frustrated.
          event.preventDefault();
          // TODO(ahe): Consider starting a compilation.
          break;
      }
    }
  
    void onShiftedKeyUp(KeyboardEvent event) {
      switch (event.keyCode) {
        case KeyCode.TAB:
          event.preventDefault();
          break;
      }
    }
  
    void onUnmodifiedKeyUp(KeyboardEvent event) {
  