Standardize usage of virtual/override/final specifiers.

ash/shelf/shelf_window_watcher_unittest.cc

Index: ash/shelf/shelf_window_watcher_unittest.cc
diff --git a/ash/shelf/shelf_window_watcher_unittest.cc b/ash/shelf/shelf_window_watcher_unittest.cc
index c5d1b728b8a9b2a9d8c0013c593e2aa70779619e..34af9ba695e138386a6ed73c0f67bae3b6de86d7 100644
--- a/ash/shelf/shelf_window_watcher_unittest.cc
+++ b/ash/shelf/shelf_window_watcher_unittest.cc
@@ -25,14 +25,14 @@ namespace ash {
 class ShelfWindowWatcherTest : public test::AshTestBase {
  public:
   ShelfWindowWatcherTest() : model_(NULL) {}
-  virtual ~ShelfWindowWatcherTest() {}
+  ~ShelfWindowWatcherTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     test::AshTestBase::SetUp();
     model_ = test::ShellTestApi(Shell::GetInstance()).shelf_model();
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     model_ = NULL;
     test::AshTestBase::TearDown();
   }