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

mojo/edk/system/parent_token_serializer_state_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_STATE_WIN_H_
 #define MOJO_EDK_SYSTEM_PARENT_TOKEN_SERIALIZER_STATE_WIN_H_
 
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/singleton.h"
@@ skipping 25 matching lines @@
                      PlatformHandle* handles) override;
 
   scoped_refptr<base::TaskRunner> token_serialize_thread() {
     return token_serialize_thread_.task_runner();
   }
 
  private:
   friend struct base::DefaultSingletonTraits<ParentTokenSerializerState>;
 
   ParentTokenSerializerState();
-  virtual ~ParentTokenSerializerState();
+  ~ParentTokenSerializerState() override;
 
   // A separate thread to handle sync IPCs from child processes for exchanging
   // platform handles with tokens. We use a separate thread because latency is
   // very sensitive (since any time a pipe is created or sent, a child process
   // makes a sync call to this class).
   base::Thread token_serialize_thread_;
 
   // Used in the parent (unsandboxed) process to hold a mapping between HANDLES
   // and tokens. When a child process wants to send a HANDLE to another process,
   // it exchanges it to a token and then the other process exchanges that token
   // back to a HANDLE.
   base::Lock lock_;  // Guards access to below.
   base::hash_map<uint64_t, HANDLE> token_map_;
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_PARENT_TOKEN_SERIALIZER_STATE_WIN_H_