Standardize usage of virtual/override/final in base/

base/sequenced_task_runner.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.
 
 #ifndef BASE_SEQUENCED_TASKRUNNER_H_
 #define BASE_SEQUENCED_TASKRUNNER_H_
 
 #include "base/base_export.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/task_runner.h"
@@ skipping 121 matching lines @@
   // and false if the object definitely will not be released.
   template <class T>
   bool ReleaseSoon(const tracked_objects::Location& from_here,
                    T* object) {
     return
         subtle::ReleaseHelperInternal<T, bool>::ReleaseViaSequencedTaskRunner(
             this, from_here, object);
   }
 
  protected:
-  virtual ~SequencedTaskRunner() {}
+  ~SequencedTaskRunner() override {}
 
  private:
   template <class T, class R> friend class subtle::DeleteHelperInternal;
   template <class T, class R> friend class subtle::ReleaseHelperInternal;
 
   bool DeleteSoonInternal(const tracked_objects::Location& from_here,
                           void(*deleter)(const void*),
                           const void* object);
 
   bool ReleaseSoonInternal(const tracked_objects::Location& from_here,
                            void(*releaser)(const void*),
                            const void* object);
 };
 
 }  // namespace base
 
 #endif  // BASE_SEQUENCED_TASKRUNNER_H_