Standardize usage of virtual/override/final specifiers.

ash/wm/video_detector_unittest.cc

Index: ash/wm/video_detector_unittest.cc
diff --git a/ash/wm/video_detector_unittest.cc b/ash/wm/video_detector_unittest.cc
index d2443da66652932c9ff09a9e44d7a1de60b85f64..d431c2c146d9b045a69b4fa981e7c6539edfdf14 100644
--- a/ash/wm/video_detector_unittest.cc
+++ b/ash/wm/video_detector_unittest.cc
@@ -40,7 +40,7 @@ class TestVideoDetectorObserver : public VideoDetectorObserver {
   }
 
   // VideoDetectorObserver implementation.
-  virtual void OnVideoDetected(bool is_fullscreen) override {
+  void OnVideoDetected(bool is_fullscreen) override {
     num_invocations_++;
     if (is_fullscreen)
       num_fullscreens_++;
@@ -64,9 +64,9 @@ class TestVideoDetectorObserver : public VideoDetectorObserver {
 class VideoDetectorTest : public AshTestBase {
  public:
   VideoDetectorTest() {}
-  virtual ~VideoDetectorTest() {}
+  ~VideoDetectorTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     AshTestBase::SetUp();
     observer_.reset(new TestVideoDetectorObserver);
     detector_ = Shell::GetInstance()->video_detector();
@@ -76,7 +76,7 @@ class VideoDetectorTest : public AshTestBase {
     detector_->set_now_for_test(now_);
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     detector_->RemoveObserver(observer_.get());
     AshTestBase::TearDown();
   }