code: function(oldName, newName) {
      var change = false;
      for (var i = 0; i < this.arguments_.length; i++) {
        if (Blockly.Names.equals(oldName, this.arguments_[i])) {
          this.arguments_[i] = newName;
          change = true;
        }
      }
      if (change) {
        this.updateParams_();
        // Update the mutator's variables if the mutator is open.
        if (this.mutator.isVisible()) {
          var blocks = this.mutator.workspace_.getAllBlocks();
          for (var i = 0, block; block = blocks[i]; i++) {
            if (block.type == 'procedures_mutatorarg' &&
                Blockly.Names.equals(oldName, block.getFieldValue('NAME'))) {
              block.setFieldValue(newName, 'NAME');
            }
          }
        }
      }
    }
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