Bad view benchmark with timing

view.cc

  int64_t before = rdtsc();
  SpawnNThreadsRunning(15, [&shared]() {
    for (int i = 0; i < reps; ++i) {
      auto snapshot = shared.Get();
      // ... do some meaningless work...
    }
  });
  for (int i = 0; i < reps; ++i) {
    auto snapshot = shared.Get();
    // ... do some meaningless work...
  }
  WaitForThreads();
  int64_t after = rdtsc();
  ReportCycles(after - before);

BENCHMARK(BM_View)->Threads(1);