Add OVERRIDE to gpu/ and gl/.

ui/gfx/gl/gl_context_cgl.h

Index: ui/gfx/gl/gl_context_cgl.h
diff --git a/ui/gfx/gl/gl_context_cgl.h b/ui/gfx/gl/gl_context_cgl.h
index af918de36ca1e3d1242821d0eaeb40d236f00feb..fdceeda34b17a1e745528a73f5390f694214a4d6 100644
--- a/ui/gfx/gl/gl_context_cgl.h
+++ b/ui/gfx/gl/gl_context_cgl.h
@@ -16,13 +16,13 @@ class GLContextCGL : public GLContext {
 
   // 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:
   void* context_;