Migrate more tests to ScopedFeatureList.

base/feature_list.h

 // Copyright 2015 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 BASE_FEATURE_LIST_H_
 #define BASE_FEATURE_LIST_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 145 matching lines @@
   // about |enable_features| and |disable_features| parameters.
   static bool InitializeInstance(const std::string& enable_features,
                                  const std::string& disable_features);
 
   // Returns the singleton instance of FeatureList. Will return null until an
   // instance is registered via SetInstance().
   static FeatureList* GetInstance();
 
   // 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.

[Ilya Sherman, 2016/11/08 00:20:00]

Maybe we should remove ClearInstanceForTesting() from the public API, to better
discourage tests from using SetInstance()?  I think we made
ClearInstanceForTesting() public prior to implementing a scoped feature list for
tests.

[Alexei Svitkine (slow), 2016/11/08 08:03:58]

It's still being used from a few places - such as test harness runners and
ScopedFeatureList itself, so we can't remove it for now unless we find
replacements for those.

   static void SetInstance(std::unique_ptr<FeatureList> instance);
 
   // Clears the previously-registered singleton instance for tests and returns
   // the old instance.
   // Note: Most tests should never call this directly. Instead consider using
   // base::test::ScopedFeatureList.
   static std::unique_ptr<FeatureList> ClearInstanceForTesting();
 
   // Sets a given (initialized) |instance| to be the singleton feature list,
   // for testing. Existing instance must be null. This is primarily intended
@@ skipping 83 matching lines @@
 
   // Whether this object has been initialized from command line.
   bool initialized_from_command_line_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(FeatureList);
 };
 
 }  // namespace base
 
 #endif  // BASE_FEATURE_LIST_H_