  int getFlagsImpl(
      folly::WriteFlags flags,
      int /*defaultFlags*/) noexcept override {
    return oldCallback_->getFlags(flags, false /*zeroCopyEnabled*/);
  }
  int getFlagsImpl(
      folly::WriteFlags flags,
      int  ) noexcept override {
    return oldCallback_->getFlags(flags, false  );
  }