Standardize usage of virtual/override/final specifiers in base/.

base/metrics/histogram_base_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 <vector>
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 class HistogramBaseTest : public testing::Test {
  protected:
   HistogramBaseTest() {
     // Each test will have a clean state (no Histogram / BucketRanges
     // registered).
     statistics_recorder_ = NULL;
     ResetStatisticsRecorder();
   }
 
-  virtual ~HistogramBaseTest() {
-    delete statistics_recorder_;
-  }
+  ~HistogramBaseTest() override { delete statistics_recorder_; }
 
   void ResetStatisticsRecorder() {
     delete statistics_recorder_;
     statistics_recorder_ = new StatisticsRecorder();
   }
 
  private:
   StatisticsRecorder* statistics_recorder_;
 };
 
@@ skipping 110 matching lines @@
 
   PickleIterator iter2(pickle);
   deserialized = DeserializeHistogramInfo(&iter2);
   EXPECT_TRUE(deserialized);
   EXPECT_NE(histogram, deserialized);
   EXPECT_EQ("TestHistogram", deserialized->histogram_name());
   EXPECT_EQ(0, deserialized->flags());
 }
 
 }  // namespace base