Standardize usage of virtual/override/final in base/

base/metrics/field_trial_unittest.cc

 // 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.
 
 #include "base/metrics/field_trial.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 26 matching lines @@
   return exploded.year;
 }
 
 // FieldTrialList::Observer implementation for testing.
 class TestFieldTrialObserver : public FieldTrialList::Observer {
  public:
   TestFieldTrialObserver() {
     FieldTrialList::AddObserver(this);
   }
 
-  virtual ~TestFieldTrialObserver() {
-    FieldTrialList::RemoveObserver(this);
-  }
+  ~TestFieldTrialObserver() override { FieldTrialList::RemoveObserver(this); }
 
-  virtual void OnFieldTrialGroupFinalized(const std::string& trial,
-                                          const std::string& group) override {
+  void OnFieldTrialGroupFinalized(const std::string& trial,
+                                  const std::string& group) override {
     trial_name_ = trial;
     group_name_ = group;
   }
 
   const std::string& trial_name() const { return trial_name_; }
   const std::string& group_name() const { return group_name_; }
 
  private:
   std::string trial_name_;
   std::string group_name_;
@@ skipping 923 matching lines @@
     EXPECT_TRUE(active_groups.empty());
 
     // The trial shouldn't be listed in the |StatesToString()| result.
     std::string states;
     FieldTrialList::StatesToString(&states);
     EXPECT_TRUE(states.empty());
   }
 }
 
 }  // namespace base