code: function(oldName, newName) {
      for (var i = 0; i < this.arguments_.length; i++) {
        if (Blockly.Names.equals(oldName, this.arguments_[i])) {
          this.arguments_[i] = newName;
          this.getField('ARGNAME' + i).setValue(newName);
        }
      }
    }
docs: Notification that a variable is renaming.
  If the name matches one of this block's variables, rename it.
  @param {string} oldName Previous name of variable.
  @param {string} newName Renamed variable.
  @this Blockly.Block