Method rend

be/src/gutil/strings/stringpiece.h:271–273

    return const_reverse_iterator(ptr_ + length_);
  }
  const_reverse_iterator rend() const {
    return const_reverse_iterator(ptr_);
  }
  // STLS says return size_type, but Google says return int
  int max_size() const { return length_; }
  int capacity() const { return length_; }