Standardize usage of virtual/override/final in mojo/

mojo/services/gles2/mojo_buffer_backing.h

 // Copyright 2014 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 MOJO_SERVICES_GLES2_MOJO_BUFFER_BACKING_H_
 #define MOJO_SERVICES_GLES2_MOJO_BUFFER_BACKING_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "gpu/command_buffer/common/buffer.h"
 #include "mojo/public/cpp/system/core.h"
 
 namespace mojo {
 namespace gles2 {
 
 class MojoBufferBacking : public gpu::BufferBacking {
  public:
   MojoBufferBacking(mojo::ScopedSharedBufferHandle handle,
                     void* memory,
                     size_t size);
-  virtual ~MojoBufferBacking();
+  ~MojoBufferBacking() override;
 
   static scoped_ptr<gpu::BufferBacking> Create(
       mojo::ScopedSharedBufferHandle handle,
       size_t size);
 
-  virtual void* GetMemory() const override;
-  virtual size_t GetSize() const override;
+  void* GetMemory() const override;
+  size_t GetSize() const override;
 
  private:
   mojo::ScopedSharedBufferHandle handle_;
   void* memory_;
   size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(MojoBufferBacking);
 };
 
 }  // namespace gles2
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_GLES2_MOJO_BUFFER_BACKING_H_