Update {virtual,override} to follow C++11 style in ppapi.

ppapi/proxy/plugin_message_filter.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 PPAPI_PROXY_PLUGIN_MESSAGE_FILTER_H_
 #define PPAPI_PROXY_PLUGIN_MESSAGE_FILTER_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 22 matching lines @@
   // |seen_instance_ids| is a pointer to a set that will be used to uniquify
   // PP_Instances across all renderer channels. The same pointer should be
   // passed to each MessageFilter to ensure uniqueness, and the value should
   // outlive this class. It could be NULL if this filter is for a browser
   // channel.
   // |thread_registrar| is used to look up handling threads for resource
   // reply messages. It shouldn't be NULL.
   PluginMessageFilter(
       std::set<PP_Instance>* seen_instance_ids,
       scoped_refptr<ResourceReplyThreadRegistrar> thread_registrar);
-  virtual ~PluginMessageFilter();
+  ~PluginMessageFilter() override;
 
   // MessageFilter implementation.
-  virtual void OnFilterAdded(IPC::Sender* sender) override;
-  virtual void OnFilterRemoved() override;
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
+  void OnFilterAdded(IPC::Sender* sender) override;
+  void OnFilterRemoved() override;
+  bool OnMessageReceived(const IPC::Message& message) override;
 
   // IPC::Sender implementation.
-  virtual bool Send(IPC::Message* msg) override;
+  bool Send(IPC::Message* msg) override;
 
   void AddResourceMessageFilter(
       const scoped_refptr<ResourceMessageFilter>& filter);
 
   // Simulates an incoming resource reply that is handled on the calling thread.
   // For testing only.
   static void DispatchResourceReplyForTest(
       const ResourceMessageReplyParams& reply_params,
       const IPC::Message& nested_msg);
 
@@ skipping 19 matching lines @@
 
   // The IPC sender to the renderer. May be NULL if we're not currently
   // attached as a filter.
   IPC::Sender* sender_;
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PLUGIN_MESSAGE_FILTER_H_