Standardize usage of virtual/override/final in base/

base/message_loop/message_loop_unittest.cc

Index: base/message_loop/message_loop_unittest.cc
diff --git a/base/message_loop/message_loop_unittest.cc b/base/message_loop/message_loop_unittest.cc
index 1a42cc62ebc18f9dc900e9e2a2e7ed276f43a3f5..733f5e5b51080b2059a646c8eb6ee3a35b22afe9 100644
--- a/base/message_loop/message_loop_unittest.cc
+++ b/base/message_loop/message_loop_unittest.cc
@@ -664,16 +664,16 @@ class DummyTaskObserver : public MessageLoop::TaskObserver {
         num_tasks_processed_(0),
         num_tasks_(num_tasks) {}
 
-  virtual ~DummyTaskObserver() {}
+  ~DummyTaskObserver() override {}
 
-  virtual void WillProcessTask(const PendingTask& pending_task) override {
+  void WillProcessTask(const PendingTask& pending_task) override {
     num_tasks_started_++;
     EXPECT_TRUE(pending_task.time_posted != TimeTicks());
     EXPECT_LE(num_tasks_started_, num_tasks_);
     EXPECT_EQ(num_tasks_started_, num_tasks_processed_ + 1);
   }
 
-  virtual void DidProcessTask(const PendingTask& pending_task) override {
+  void DidProcessTask(const PendingTask& pending_task) override {
     num_tasks_processed_++;
     EXPECT_TRUE(pending_task.time_posted != TimeTicks());
     EXPECT_LE(num_tasks_started_, num_tasks_);
@@ -756,10 +756,10 @@ namespace {
 
 class QuitDelegate : public MessageLoopForIO::Watcher {
  public:
-  virtual void OnFileCanWriteWithoutBlocking(int fd) override {
+  void OnFileCanWriteWithoutBlocking(int fd) override {
     MessageLoop::current()->QuitWhenIdle();
   }
-  virtual void OnFileCanReadWithoutBlocking(int fd) override {
+  void OnFileCanReadWithoutBlocking(int fd) override {
     MessageLoop::current()->QuitWhenIdle();
   }
 };
@@ -857,7 +857,7 @@ class MLDestructionObserver : public MessageLoop::DestructionObserver {
         destruction_observer_called_(destruction_observer_called),
         task_destroyed_before_message_loop_(false) {
   }
-  virtual void WillDestroyCurrentMessageLoop() override {
+  void WillDestroyCurrentMessageLoop() override {
     task_destroyed_before_message_loop_ = *task_destroyed_;
     *destruction_observer_called_ = true;
   }