Standardize usage of virtual/override/final in mojo/

mojo/edk/system/channel.h

 // Copyright 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.
 
 #ifndef MOJO_EDK_SYSTEM_CHANNEL_H_
 #define MOJO_EDK_SYSTEM_CHANNEL_H_
 
 #include <stdint.h>
 
 #include "base/containers/hash_tables.h"
@@ skipping 110 matching lines @@
 
   // See |RawChannel::GetSerializedPlatformHandleSize()|.
   size_t GetSerializedPlatformHandleSize() const;
 
   embedder::PlatformSupport* platform_support() const {
     return platform_support_;
   }
 
  private:
   friend class base::RefCountedThreadSafe<Channel>;
-  virtual ~Channel();
+  ~Channel() override;
 
   // |RawChannel::Delegate| implementation (only called on the creation thread):
-  virtual void OnReadMessage(
+  void OnReadMessage(
       const MessageInTransit::View& message_view,
       embedder::ScopedPlatformHandleVectorPtr platform_handles) override;
-  virtual void OnError(Error error) override;
+  void OnError(Error error) override;
 
   // Helpers for |OnReadMessage| (only called on the creation thread):
   void OnReadMessageForDownstream(
       const MessageInTransit::View& message_view,
       embedder::ScopedPlatformHandleVectorPtr platform_handles);
   void OnReadMessageForChannel(
       const MessageInTransit::View& message_view,
       embedder::ScopedPlatformHandleVectorPtr platform_handles);
 
   // Handles "attach and run endpoint" messages.
@@ skipping 50 matching lines @@
   // if/when we wrap).
   RemoteChannelEndpointIdGenerator remote_id_generator_;
 
   DISALLOW_COPY_AND_ASSIGN(Channel);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_CHANNEL_H_