NaCl: Fix Chromium style warnings in src/trusted/plugin/

ppapi/native_client/src/trusted/plugin/module_ppapi.h

 /*
  * Copyright (c) 2013 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 "ppapi/c/private/ppb_nacl_private.h"
 #include "ppapi/cpp/module.h"
 
 namespace plugin {
 
 class ModulePpapi : public pp::Module {
  public:
   ModulePpapi();
 
-  virtual ~ModulePpapi();
+  ~ModulePpapi() override;
 
-  virtual bool Init();
+  bool Init() override;
 
-  virtual pp::Instance* CreateInstance(PP_Instance pp_instance);
+  pp::Instance* CreateInstance(PP_Instance pp_instance) override;
 
  private:
   bool init_was_successful_;
   const PPB_NaCl_Private* private_interface_;
 };
 
 }  // namespace plugin
 
 
 namespace pp {
 
 Module* CreateModule();
 
 }  // namespace pp