Do not instantiate base::FieldTrialList explicitly in tests

The test suite already instantiates a FieldTrialList as per
https://chromium-review.googlesource.com/c/chromium/src/+/1883567 so
it's no longer necessary to do so explicitly in tests.

This patch addresses unit tests under:
/components/data_reduction_proxy

This CL was uploaded by git cl split.

Bug: 1018667
Change-Id: I9685de8a0463ad7645e27d21474511ed8a030e99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1916468Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Auto-Submit: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719343}

components/data_reduction_proxy/core/browser/data_reduction_proxy_config_unittest.cc

@@ -213,7 +213,6 @@ class DataReductionProxyConfigTest : public testing::Test {
 };
 
 TEST_F(DataReductionProxyConfigTest, TestReloadConfigHoldback) {
-  base::FieldTrialList field_trial_list(nullptr);
   ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
       "DataCompressionProxyHoldback", "Enabled"));
 
@@ -405,6 +404,9 @@ TEST_F(DataReductionProxyConfigTest, DISABLED_WarmupURL) {
 
     ResetSettings();
 
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
+
     variations::testing::ClearAllVariationParams();
     std::map<std::string, std::string> variation_params;
 
@@ -413,7 +415,6 @@ TEST_F(DataReductionProxyConfigTest, DISABLED_WarmupURL) {
     ASSERT_TRUE(variations::AssociateVariationParams(
         params::GetQuicFieldTrialName(), "Enabled", variation_params));
 
-    base::FieldTrialList field_trial_list(nullptr);
     base::FieldTrialList::CreateFieldTrial(params::GetQuicFieldTrialName(),
                                            "Enabled");
 

components/data_reduction_proxy/core/browser/data_reduction_proxy_service_unittest.cc

@@ -130,7 +130,6 @@ TEST_F(DataReductionProxyServiceTest, TestResetBadProxyListOnDisableDataSaver) {
 }
 
 TEST_F(DataReductionProxyServiceTest, HoldbackConfiguresProxies) {
-  base::FieldTrialList field_trial_list(nullptr);
   ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
       "DataCompressionProxyHoldback", "Enabled"));
   std::unique_ptr<DataReductionProxyTestContext> drp_test_context =

components/data_reduction_proxy/core/common/data_reduction_proxy_params_unittest.cc

@@ -201,6 +201,9 @@ TEST_F(DataReductionProxyParamsTest, QuicFieldTrial) {
     ASSERT_FALSE(base::CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kDisableDataReductionProxyWarmupURLFetch));
 
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
+
     variations::testing::ClearAllVariationParams();
     std::map<std::string, std::string> variation_params;
     if (!test.enable_warmup_url)
@@ -214,7 +217,6 @@ TEST_F(DataReductionProxyParamsTest, QuicFieldTrial) {
         params::GetQuicFieldTrialName(), test.trial_group_name,
         variation_params));
 
-    base::FieldTrialList field_trial_list(nullptr);
     base::FieldTrialList::CreateFieldTrial(params::GetQuicFieldTrialName(),
                                            test.trial_group_name);
 
@@ -275,6 +277,9 @@ TEST_F(DataReductionProxyParamsTest, QuicEnableNonCoreProxies) {
   };
 
   for (const auto& test : tests) {
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
+
     variations::testing::ClearAllVariationParams();
     std::map<std::string, std::string> variation_params;
 
@@ -282,7 +287,6 @@ TEST_F(DataReductionProxyParamsTest, QuicEnableNonCoreProxies) {
         params::GetQuicFieldTrialName(), test.trial_group_name,
         variation_params));
 
-    base::FieldTrialList field_trial_list(nullptr);
     base::FieldTrialList::CreateFieldTrial(params::GetQuicFieldTrialName(),
                                            test.trial_group_name);
 
@@ -302,7 +306,8 @@ TEST_F(DataReductionProxyParamsTest, HoldbackEnabledFieldTrial) {
   };
 
   for (const auto& test : tests) {
-    base::FieldTrialList field_trial_list(nullptr);
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
 
     ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
         "DataCompressionProxyHoldback", test.trial_group_name));
@@ -324,7 +329,8 @@ TEST_F(DataReductionProxyParamsTest, PromoFieldTrial) {
   };
 
   for (const auto& test : tests) {
-    base::FieldTrialList field_trial_list(nullptr);
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
 
     ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
         "DataCompressionProxyPromoVisibility", test.trial_group_name));
@@ -345,7 +351,8 @@ TEST_F(DataReductionProxyParamsTest, FREPromoFieldTrial) {
   };
 
   for (const auto& test : tests) {
-    base::FieldTrialList field_trial_list(nullptr);
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.Init();
 
     ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
         "DataReductionProxyFREPromo", test.trial_group_name));