Standardize usage of virtual/override/final specifiers.

ash/wm/gestures/overview_gesture_handler_unittest.cc

Index: ash/wm/gestures/overview_gesture_handler_unittest.cc
diff --git a/ash/wm/gestures/overview_gesture_handler_unittest.cc b/ash/wm/gestures/overview_gesture_handler_unittest.cc
index 6c1412bf9f1cfca3a0519ea6c9a8c4d6c004b0f6..b5a8796606f253c76eb02769131ed2ed6c23b0b1 100644
--- a/ash/wm/gestures/overview_gesture_handler_unittest.cc
+++ b/ash/wm/gestures/overview_gesture_handler_unittest.cc
@@ -18,7 +18,7 @@ namespace ash {
 class OverviewGestureHandlerTest : public test::AshTestBase {
  public:
   OverviewGestureHandlerTest() {}
-  virtual ~OverviewGestureHandlerTest() {}
+  ~OverviewGestureHandlerTest() override {}
 
   aura::Window* CreateWindow(const gfx::Rect& bounds) {
     return CreateTestWindowInShellWithDelegate(&delegate_, -1, bounds);