Standardize usage of virtual/override/final in mojo/

mojo/public/cpp/utility/tests/thread_unittest.cc

 // Copyright 2014 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 "mojo/public/cpp/utility/thread.h"
 
 #include "mojo/public/cpp/system/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace {
 
 class SetIntThread : public Thread {
  public:
   SetIntThread(int* int_to_set, int value)
       : int_to_set_(int_to_set),
         value_(value) {
   }
   SetIntThread(const Options& options, int* int_to_set, int value)
       : Thread(options),
         int_to_set_(int_to_set),
         value_(value) {
   }
 
-  virtual ~SetIntThread() {
-  }
+  ~SetIntThread() override {}
 
-  virtual void Run() override { *int_to_set_ = value_; }
+  void Run() override { *int_to_set_ = value_; }
 
  private:
   int* const int_to_set_;
   const int value_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(SetIntThread);
 };
 
 TEST(ThreadTest, CreateAndJoin) {
   int value = 0;
@@ skipping 59 matching lines @@
     options.set_stack_size(static_cast<size_t>(-1));
     SetIntThread thread(options, &value, 4);
     thread.Start();
     thread.Join();
   }, "");
 }
 #endif  // !defined(NDEBUG)
 
 }  // namespace
 }  // namespace mojo