Standardize usage of virtual/override/final in mojo/

mojo/services/native_viewport/gpu_impl.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.
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "mojo/public/cpp/bindings/interface_impl.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/services/public/interfaces/geometry/geometry.mojom.h"
 #include "mojo/services/public/interfaces/gpu/command_buffer.mojom.h"
 #include "mojo/services/public/interfaces/gpu/gpu.mojom.h"
 
 namespace gfx {
 class GLShareGroup;
 }
 
 namespace gpu {
 namespace gles2 {
 class MailboxManager;
 }
 }
 
 namespace mojo {
 
 class GpuImpl : public InterfaceImpl<Gpu> {
  public:
   GpuImpl(const scoped_refptr<gfx::GLShareGroup>& share_group,
           const scoped_refptr<gpu::gles2::MailboxManager> mailbox_manager);
 
-  virtual ~GpuImpl();
+  ~GpuImpl() override;
 
-  virtual void CreateOnscreenGLES2Context(
+  void CreateOnscreenGLES2Context(
       uint64_t native_viewport_id,
       SizePtr size,
       InterfaceRequest<CommandBuffer> command_buffer_request) override;
 
-  virtual void CreateOffscreenGLES2Context(
+  void CreateOffscreenGLES2Context(
       InterfaceRequest<CommandBuffer> command_buffer_request) override;
 
  private:
   // We need to share these across all NativeViewport instances so that contexts
   // they create can share resources with each other via mailboxes.
   scoped_refptr<gfx::GLShareGroup> share_group_;
   scoped_refptr<gpu::gles2::MailboxManager> mailbox_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuImpl);
 };
 
 }  // namespace mojo