Add OVERRIDE to gpu/ and gl/.

ui/gfx/gl/gl_surface_stub.h

 // Copyright (c) 2011 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_GFX_GL_GL_SURFACE_STUB_H_
 #define UI_GFX_GL_GL_SURFACE_STUB_H_
 #pragma once
 
 #include "ui/gfx/gl/gl_surface.h"
 
 namespace gfx {
 
 // A GLSurface that does nothing for unit tests.
 class GL_EXPORT GLSurfaceStub : public GLSurface {
  public:
   virtual ~GLSurfaceStub();
 
   void SetSize(const gfx::Size& size) { size_ = size; }
 
   // Implement GLSurface.
-  virtual void Destroy();
-  virtual bool IsOffscreen();
-  virtual bool SwapBuffers();
-  virtual gfx::Size GetSize();
-  virtual void* GetHandle();
+  virtual void Destroy() OVERRIDE;
+  virtual bool IsOffscreen() OVERRIDE;
+  virtual bool SwapBuffers() OVERRIDE;
+  virtual gfx::Size GetSize() OVERRIDE;
+  virtual void* GetHandle() OVERRIDE;
 
  private:
   gfx::Size size_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GL_GL_SURFACE_STUB_H_