Add a ScopedFeatureList class for testing and start using it.

components/ssl_config/ssl_config_service_manager_pref_unittest.cc

Index: components/ssl_config/ssl_config_service_manager_pref_unittest.cc
diff --git a/components/ssl_config/ssl_config_service_manager_pref_unittest.cc b/components/ssl_config/ssl_config_service_manager_pref_unittest.cc
index ec2aefa533869a9e08efc843dda91a236424d04c..cecdb8efdc83e8616e22eb2d3365db47357bd284 100644
--- a/components/ssl_config/ssl_config_service_manager_pref_unittest.cc
+++ b/components/ssl_config/ssl_config_service_manager_pref_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_feature_list.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "components/prefs/testing_pref_service.h"
@@ -181,10 +182,8 @@ TEST_F(SSLConfigServiceManagerPrefTest, NoSSL3) {
 // Tests that DHE may be re-enabled via features.
 TEST_F(SSLConfigServiceManagerPrefTest, DHEFeature) {
   // Toggle the feature.
-  base::FeatureList::ClearInstanceForTesting();
-  std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
-  feature_list->InitializeFromCommandLine("DHECiphers", std::string());
-  base::FeatureList::SetInstance(std::move(feature_list));
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitFromCommandLine("DHECiphers", std::string());
 
   TestingPrefServiceSimple local_state;
   SSLConfigServiceManager::RegisterPrefs(local_state.registry());