code: private String getReplacementName(String oldName) {
      for (Renamer renamer : renamerStack) {
        String newName = renamer.getReplacementName(oldName);
        if (newName != null) {
          return newName;
        }
      }
      return null;
    }
docs: Walks the stack of name maps and finds the replacement name for the
  current scope.