Migrate more tests to ScopedFeatureList.

base/feature_list.h

Index: base/feature_list.h
diff --git a/base/feature_list.h b/base/feature_list.h
index 698ecd533423e06c85a6748bd7d85ab23a46fb96..80209ba6588464d769d48215d4ffc54f23d6ac3b 100644
--- a/base/feature_list.h
+++ b/base/feature_list.h
@@ -163,6 +163,8 @@ class BASE_EXPORT FeatureList {
 
   // Registers the given |instance| to be the singleton feature list for this
   // process. This should only be called once and |instance| must not be null.
+  // Note: If you are considering using this for the purposes of testing, take
+  // a look at using base/test/scoped_feature_list.h instead.
   static void SetInstance(std::unique_ptr<FeatureList> instance);
 
   // Clears the previously-registered singleton instance for tests and returns