Standardize usage of virtual/override/final specifiers.

ash/system/overview/overview_button_tray_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 "ash/system/overview/overview_button_tray.h"
 
 #include "ash/display/display_manager.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_types.h"
 #include "ash/shelf/shelf_widget.h"
@@ skipping 22 matching lines @@
 OverviewButtonTray* GetSecondaryTray() {
   return StatusAreaWidgetTestHelper::GetSecondaryStatusAreaWidget()->
       overview_button_tray();
 }
 
 }  // namespace
 
 class OverviewButtonTrayTest : public test::AshTestBase {
  public:
   OverviewButtonTrayTest() {}
-  virtual ~OverviewButtonTrayTest() {}
+  ~OverviewButtonTrayTest() override {}
 
  protected:
   views::ImageView* GetImageView(OverviewButtonTray* tray) {
     return tray->icon_;
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OverviewButtonTrayTest);
 };
 
@@ skipping 96 matching lines @@
       Shell::GetInstance()->window_selector_controller()->IsSelecting());
   EXPECT_TRUE(GetTray()->draw_background_as_active());
 
   Shell::GetInstance()->window_selector_controller()->OnSelectionEnded();
   EXPECT_FALSE(
       Shell::GetInstance()->window_selector_controller()->IsSelecting());
   EXPECT_FALSE(GetTray()->draw_background_as_active());
 }
 
 }  // namespace ash