Fix broken clockstate.network2 histogram and add unit test

components/network_time/network_time_test_utils.h

+// Copyright 2016 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.
+
+#ifndef COMPONENTS_NETWORK_TIME_NETWORK_TIME_TEST_UTILS_H_
+#define COMPONENTS_NETWORK_TIME_NETWORK_TIME_TEST_UTILS_H_
+
+#include <map>
+#include <memory>
+
+#include "base/macros.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace test {
+class ScopedFeatureList;
+};  // namespace test
+
+class FieldTrialList;
+}  // namespace base
+
+namespace network_time {
+// A test fixture that allows configuring the network time queries field trial.
+class FieldTrialTest : public ::testing::Test {
+ public:
+  FieldTrialTest();
+  ~FieldTrialTest() override;
+
+ protected:
+  void SetNetworkQueriesWithVariationsService(bool enable,
+                                              float query_probability);
+
+ private:
+  std::unique_ptr<base::FieldTrialList> field_trial_list_;
+  std::unique_ptr<base::test::ScopedFeatureList> scoped_feature_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FieldTrialTest);
+};
+
+}  // namespace network_time
+
+#endif  // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TEST_UTILS_H_