Convert FieldTrialList to Accept a std::unique_ptr

base/metrics/field_trial.h

 // 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.
 
 // FieldTrial is a class for handling details of statistical experiments
 // performed by actual users in the field (i.e., in a shipped or beta product).
 // All code is called exclusively on the UI thread currently.
 //
 // The simplest example is an experiment to see whether one of two options
 // produces "better" results across our user population.  In that scenario, UMA
@@ skipping 40 matching lines @@
 
 //------------------------------------------------------------------------------
 
 #ifndef BASE_METRICS_FIELD_TRIAL_H_
 #define BASE_METRICS_FIELD_TRIAL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
+#include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/strings/string_piece.h"
@@ skipping 260 matching lines @@
     // Notify observers when FieldTrials's group is selected.
     virtual void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                             const std::string& group_name) = 0;
 
    protected:
     virtual ~Observer();
   };
 
   // This singleton holds the global list of registered FieldTrials.
   //
-  // To support one-time randomized field trials, specify a non-NULL
+  // To support one-time randomized field trials, specify a non-nullptr
   // |entropy_provider| which should be a source of uniformly distributed
-  // entropy values. Takes ownership of |entropy_provider|. If one time
-  // randomization is not desired, pass in NULL for |entropy_provider|.
-  explicit FieldTrialList(const FieldTrial::EntropyProvider* entropy_provider);
+  // entropy values. If one time randomization is not desired, pass in nullptr

[Alexei Svitkine (slow), 2016/09/21 15:52:00]

Nit: I think in comments just using "null" rather than "nullptr" is preferred -
since it's talking about the concept of null. I remember that was the conclusion
from the chromium-dev@ thread where we first discussed using nullptr in Chromium
instead of NULL.

[robliao, 2016/09/21 17:24:29]

Change this to lowercase null then to deemphasize the use of NULL.

+  // for |entropy_provider|.
+  explicit FieldTrialList(
+      std::unique_ptr<const FieldTrial::EntropyProvider> entropy_provider);
 
   // Destructor Release()'s references to all registered FieldTrial instances.
   ~FieldTrialList();
 
   // Get a FieldTrial instance from the factory.
   //
   // |name| is used to register the instance with the FieldTrialList class,
   // and can be used to find the trial (only one trial can be present for each
   // name). |default_group_name| is the name of the default group which will
   // be chosen if none of the subsequent appended groups get to be chosen.
@@ skipping 166 matching lines @@
 
   // List of observers to be notified when a group is selected for a FieldTrial.
   scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialList);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_H_