Adding Google benchmarking library.

base/containers/containers_benchmarks.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <algorithm>
+#include <array>
+#include <iterator>
+#include <numeric>
+#include <set>
+
+#include "base/containers/flat_set.h"
+#include "third_party/google_benchmark/include/benchmark/benchmark.h"
+
+namespace {
+
+template <typename>
+struct TypeTag {};
+
+base::flat_set<int> GenerateSet(const std::vector<int>& input,
+                                TypeTag<base::flat_set<int>>) {
+  return {input.begin(), input.end(), base::KEEP_FIRST_OF_DUPES};
+}
+
+std::set<int> GenerateSet(const std::vector<int>& input,
+                          TypeTag<std::set<int>>) {
+  return {input.begin(), input.end()};
+}
+
+template <typename Set>
+void InsertInTheBeginingByOne(benchmark::State& state) {
+  constexpr int kNewElementsCount = 10;
+  std::array<int, kNewElementsCount> new_elements;
+  std::iota(new_elements.begin(), new_elements.end(), 0);
+  std::vector<int> already_in(state.range(0));
+  std::iota(already_in.begin(), already_in.end(), kNewElementsCount);
+
+  while (state.KeepRunning()) {
+    state.PauseTiming();
+    Set test_set = GenerateSet(already_in, TypeTag<Set>{});
+    state.ResumeTiming();
+    std::copy(new_elements.begin(), new_elements.end(),
+              std::inserter(test_set, test_set.begin()));
+  }
+}
+
+constexpr int kMinSize = 0;
+constexpr int kMaxSize = 1 << 10;
+
+BENCHMARK_TEMPLATE(InsertInTheBeginingByOne, std::set<int>)
+    ->Range(kMinSize, kMaxSize);
+BENCHMARK_TEMPLATE(InsertInTheBeginingByOne, base::flat_set<int>)
+    ->Range(kMinSize, kMaxSize);
+
+}  // namespace