Add a ScopedFeatureList class for testing and start using it.

components/variations/service/variations_service_unittest.cc

 // Copyright (c) 2012 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 "components/variations/service/variations_service.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <utility>
@@ skipping 254 matching lines @@
  private:
   base::MessageLoop message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsServiceTest);
 };
 
 TEST_F(VariationsServiceTest, CreateTrialsFromSeed) {
   TestingPrefServiceSimple prefs;
   VariationsService::RegisterPrefs(prefs.registry());
 
-  // Setup base::FeatureList.
-  base::FeatureList::ClearInstanceForTesting();
-  base::FeatureList::SetInstance(base::WrapUnique(new base::FeatureList()));
-
   // Create a local base::FieldTrialList, to hold the field trials created in
   // this test.
   base::FieldTrialList field_trial_list(nullptr);
 
   // Create a variations service.
   TestVariationsService service(
       base::WrapUnique(new web_resource::TestRequestAllowedNotifier(&prefs)),
       &prefs);
   service.SetCreateTrialsFromSeedCalledForTesting(false);
 
   // Store a seed.
   service.StoreSeed(SerializeSeed(CreateTestSeed()), std::string(),
                     std::string(), base::Time::Now(), false, false);
   prefs.SetInt64(prefs::kVariationsLastFetchTime,
                  base::Time::Now().ToInternalValue());
 
   // Check that field trials are created from the seed. Since the test study has
   // only 1 experiment with 100% probability weight, we must be part of it.
   EXPECT_TRUE(service.CreateTrialsFromSeed(base::FeatureList::GetInstance()));
   EXPECT_EQ(kTestSeedExperimentName,
             base::FieldTrialList::FindFullName(kTestSeedStudyName));
 }
 
 TEST_F(VariationsServiceTest, CreateTrialsFromSeedNoLastFetchTime) {
   TestingPrefServiceSimple prefs;
   VariationsService::RegisterPrefs(prefs.registry());
 
-  // Setup base::FeatureList.
-  base::FeatureList::ClearInstanceForTesting();
-  base::FeatureList::SetInstance(base::WrapUnique(new base::FeatureList()));
-
   // Create a local base::FieldTrialList, to hold the field trials created in
   // this test.
   base::FieldTrialList field_trial_list(nullptr);
 
   // Create a variations service
   TestVariationsService service(
       base::WrapUnique(new web_resource::TestRequestAllowedNotifier(&prefs)),
       &prefs);
   service.SetCreateTrialsFromSeedCalledForTesting(false);
 
   // Store a seed. To simulate a first run, |prefs::kVariationsLastFetchTime|
   // is left empty.
   service.StoreSeed(SerializeSeed(CreateTestSeed()), std::string(),
                     std::string(), base::Time::Now(), false, false);
   EXPECT_EQ(0, prefs.GetInt64(prefs::kVariationsLastFetchTime));
 
   // Check that field trials are created from the seed. Since the test study has
   // only 1 experiment with 100% probability weight, we must be part of it.
   EXPECT_TRUE(service.CreateTrialsFromSeed(base::FeatureList::GetInstance()));
   EXPECT_EQ(base::FieldTrialList::FindFullName(kTestSeedStudyName),
             kTestSeedExperimentName);
 }
 
 TEST_F(VariationsServiceTest, CreateTrialsFromOutdatedSeed) {
   TestingPrefServiceSimple prefs;
   VariationsService::RegisterPrefs(prefs.registry());
 
-  // Setup base::FeatureList.
-  base::FeatureList::ClearInstanceForTesting();
-  base::FeatureList::SetInstance(base::WrapUnique(new base::FeatureList()));
-
   // Create a local base::FieldTrialList, to hold the field trials created in
   // this test.
   base::FieldTrialList field_trial_list(nullptr);
 
   // Create a variations service.
   TestVariationsService service(
       base::WrapUnique(new web_resource::TestRequestAllowedNotifier(&prefs)),
       &prefs);
   service.SetCreateTrialsFromSeedCalledForTesting(false);
 
@@ skipping 439 matching lines @@
     }
     const base::ListValue* pref_value =
         prefs.GetList(prefs::kVariationsPermanentConsistencyCountry);
     EXPECT_EQ(ListValueToString(expected_list_value),
               ListValueToString(*pref_value))
         << test.pref_value_before << ", " << test.country_code_override;
   }
 }
 
 }  // namespace variations