Standardize usage of virtual/override/final in ui/

ui/gl/gl_osmesa_api_implementation.h

 // Copyright (c) 2012 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 UI_GL_GL_OSMESA_API_IMPLEMENTATION_H_
 #define UI_GL_GL_OSMESA_API_IMPLEMENTATION_H_
 
 #include "base/compiler_specific.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_export.h"
 
 namespace gfx {
 
 class GLContext;
 
 void InitializeStaticGLBindingsOSMESA();
 void InitializeDynamicGLBindingsOSMESA(GLContext* context);
 void InitializeDebugGLBindingsOSMESA();
 void ClearGLBindingsOSMESA();
 
 class GL_EXPORT OSMESAApiBase : public OSMESAApi {
  public:
   // Include the auto-generated part of this class. We split this because
   // it means we can easily edit the non-auto generated parts right here in
   // this file instead of having to edit some template or the code generator.
   #include "gl_bindings_api_autogen_osmesa.h"
 
  protected:
   OSMESAApiBase();
-  virtual ~OSMESAApiBase();
+  ~OSMESAApiBase() override;
   void InitializeBase(DriverOSMESA* driver);
 
   DriverOSMESA* driver_;
 };
 
 class GL_EXPORT RealOSMESAApi : public OSMESAApiBase {
  public:
   RealOSMESAApi();
-  virtual ~RealOSMESAApi();
+  ~RealOSMESAApi() override;
   void Initialize(DriverOSMESA* driver);
 };
 
 // Inserts a TRACE for every OSMESA call.
 class GL_EXPORT TraceOSMESAApi : public OSMESAApi {
  public:
   TraceOSMESAApi(OSMESAApi* osmesa_api) : osmesa_api_(osmesa_api) { }
-  virtual ~TraceOSMESAApi();
+  ~TraceOSMESAApi() override;
 
   // Include the auto-generated part of this class. We split this because
   // it means we can easily edit the non-auto generated parts right here in
   // this file instead of having to edit some template or the code generator.
   #include "gl_bindings_api_autogen_osmesa.h"
 
  private:
   OSMESAApi* osmesa_api_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_OSMESA_API_IMPLEMENTATION_H_