Method capacity

be/src/gutil/strings/stringpiece.h:276–276

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

  // cpplint.py emits a false positive [build/include_what_you_use]
  int copy(char* buf, size_type n, size_type pos = 0) const;  // NOLINT