Add OVERRIDE to gpu/ and gl/.

ui/gfx/gl/gl_context_osmesa.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_CONTEXT_OSMESA_H_
 #define UI_GFX_GL_GL_CONTEXT_OSMESA_H_
 #pragma once
 
 #include "ui/gfx/gl/gl_context.h"
 
 typedef struct osmesa_context *OSMesaContext;
 
 namespace gfx {
 
 class GLShareGroup;
 class GLSurface;
 
 // Encapsulates an OSMesa OpenGL context that uses software rendering.
 class GLContextOSMesa : public GLContext {
  public:
   explicit GLContextOSMesa(GLShareGroup* share_group);
   virtual ~GLContextOSMesa();
 
   // Implement GLContext.
   virtual bool Initialize(
-      GLSurface* compatible_surface, GpuPreference gpu_preference);
-  virtual void Destroy();
-  virtual bool MakeCurrent(GLSurface* surface);
-  virtual void ReleaseCurrent(GLSurface* surface);
-  virtual bool IsCurrent(GLSurface* surface);
-  virtual void* GetHandle();
-  virtual void SetSwapInterval(int interval);
+      GLSurface* compatible_surface, GpuPreference gpu_preference) OVERRIDE;
+  virtual void Destroy() OVERRIDE;
+  virtual bool MakeCurrent(GLSurface* surface) OVERRIDE;
+  virtual void ReleaseCurrent(GLSurface* surface) OVERRIDE;
+  virtual bool IsCurrent(GLSurface* surface) OVERRIDE;
+  virtual void* GetHandle() OVERRIDE;
+  virtual void SetSwapInterval(int interval) OVERRIDE;
 
  private:
   OSMesaContext context_;
 
   DISALLOW_COPY_AND_ASSIGN(GLContextOSMesa);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GL_GL_CONTEXT_OSMESA_H_