Method operator()

src/butil/strings/string_util.h:121–123

template<typename Char> struct CaseInsensitiveCompareASCII {
 public:
  bool operator()(Char x, Char y) const {
    return ToLowerASCII(x) == ToLowerASCII(y);
  }
};

// These threadsafe functions return references to globally unique empty