Fix clang/win build after https://codereview.chromium.org/1471123002

mojo/edk/system/parent_token_serializer_win.h

 // Copyright 2015 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_PARENT_TOKEN_SERIALIZER_WIN_H_
 #define MOJO_EDK_SYSTEM_PARENT_TOKEN_SERIALIZER_WIN_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 11 matching lines @@
     : NON_EXPORTED_BASE(public base::MessageLoopForIO::IOHandler) {
  public:
   // |child_process| is a handle to the child process. It's not owned by this
   // class but is guaranteed to be alive as long as the child process is
   // running. |pipe| is a handle to the communication pipe to the child process,
   // which is generated inside mojo::edk::ChildProcessLaunched. It is owned by
   // this class.
   ParentTokenSerializer(HANDLE child_process, ScopedPlatformHandle pipe);
 
  private:
-  virtual ~ParentTokenSerializer();
+  virtual ~ParentTokenSerializer() override;
 
   void RegisterIOHandler();
   void BeginRead();
 
   void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
                      DWORD bytes_transferred,
                      DWORD error) override;
 
   // Helper wrappers around DuplicateHandle.
   HANDLE DuplicateToChild(HANDLE handle);
   HANDLE DuplicateFromChild(HANDLE handle);
 
   HANDLE child_process_;
   ScopedPlatformHandle pipe_;
   base::MessageLoopForIO::IOContext read_context_;
   base::MessageLoopForIO::IOContext write_context_;
 
   std::vector<char> read_data_;
   // How many bytes in read_data_ we already read.
   uint32_t num_bytes_read_;
   std::vector<char> write_data_;
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_PARENT_TOKEN_SERIALIZER_WIN_H_