Standardize usage of virtual/override/final specifiers.

ash/system/chromeos/tray_tracing.h

 // Copyright 2013 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.
 
 #ifndef ASH_SYSTEM_TRAY_TRACING_H_
 #define ASH_SYSTEM_TRAY_TRACING_H_
 
 #include "ash/ash_export.h"
 #include "ash/system/tray/tray_image_item.h"
 
@@ skipping 11 matching lines @@
   virtual void OnTracingModeChanged(bool value) = 0;
 };
 
 // This is the item that displays when users enable performance tracing at
 // chrome://slow.  It alerts them that this mode is running, and provides an
 // easy way to open the page to disable it.
 class TrayTracing : public TrayImageItem,
                     public TracingObserver {
  public:
   explicit TrayTracing(SystemTray* system_tray);
-  virtual ~TrayTracing();
+  ~TrayTracing() override;
 
  private:
   void SetTrayIconVisible(bool visible);
 
   // Overridden from TrayImageItem.
-  virtual bool GetInitialVisibility() override;
-  virtual views::View* CreateDefaultView(user::LoginStatus status) override;
-  virtual views::View* CreateDetailedView(user::LoginStatus status) override;
-  virtual void DestroyDefaultView() override;
-  virtual void DestroyDetailedView() override;
+  bool GetInitialVisibility() override;
+  views::View* CreateDefaultView(user::LoginStatus status) override;
+  views::View* CreateDetailedView(user::LoginStatus status) override;
+  void DestroyDefaultView() override;
+  void DestroyDetailedView() override;
 
   // Overridden from TracingObserver.
-  virtual void OnTracingModeChanged(bool value) override;
+  void OnTracingModeChanged(bool value) override;
 
   views::View* default_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayTracing);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_TRACING_H_