Adding Google benchmarking library.

third_party/google_benchmark/src/benchmark_api_internal.h

Index: third_party/google_benchmark/src/benchmark_api_internal.h
diff --git a/third_party/google_benchmark/src/benchmark_api_internal.h b/third_party/google_benchmark/src/benchmark_api_internal.h
new file mode 100644
index 0000000000000000000000000000000000000000..c2208737c3722f810ff5a92c81d140d92f2b2bf4
--- /dev/null
+++ b/third_party/google_benchmark/src/benchmark_api_internal.h
@@ -0,0 +1,46 @@
+#ifndef BENCHMARK_API_INTERNAL_H
+#define BENCHMARK_API_INTERNAL_H
+
+#include "benchmark/benchmark_api.h"
+
+#include <cmath>
+#include <iosfwd>
+#include <limits>
+#include <string>
+#include <vector>
+
+namespace benchmark {
+namespace internal {
+
+// Information kept per benchmark we may want to run
+struct Benchmark::Instance {
+  std::string name;
+  Benchmark* benchmark;
+  ReportMode report_mode;
+  std::vector<int> arg;
+  TimeUnit time_unit;
+  int range_multiplier;
+  bool use_real_time;
+  bool use_manual_time;
+  BigO complexity;
+  BigOFunc* complexity_lambda;
+  UserCounters counters;
+  bool last_benchmark_instance;
+  int repetitions;
+  double min_time;
+  size_t iterations;
+  int threads;  // Number of concurrent threads to us
+};
+
+bool FindBenchmarksInternal(const std::string& re,
+                            std::vector<Benchmark::Instance>* benchmarks,
+                            std::ostream* Err);
+
+bool IsZero(double n);
+
+ConsoleReporter::OutputOptions GetOutputOptions(bool force_no_color = false);
+
+}  // end namespace internal
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_API_INTERNAL_H