code: private boolean isPropertyDeclaredConstant(
        ObjectType objectType, String prop) {
      if (enforceCodingConventions
          && compiler.getCodingConvention().isConstant(prop)) {
        return true;
      }
      for (; objectType != null; objectType = objectType.getImplicitPrototype()) {
        JSDocInfo docInfo = objectType.getOwnPropertyJSDocInfo(prop);
        if (docInfo != null && docInfo.isConstant()) {
          return true;
        }
      }
      return false;
    }
docs: Returns if a property is declared constant.