Change common_message_generator code block.

ipc/param_traits_write_macros.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 IPC_PARAM_TRAITS_WRITE_MACROS_H_
 #define IPC_PARAM_TRAITS_WRITE_MACROS_H_
+#pragma once
 
 // Null out all the macros that need nulling.
 #include "ipc/ipc_message_null_macros.h"
 
 // STRUCT declarations cause corresponding STRUCT_TRAITS declarations to occur.
 #undef IPC_STRUCT_BEGIN
 #undef IPC_STRUCT_MEMBER
 #undef IPC_STRUCT_END
 #define IPC_STRUCT_BEGIN(struct_name) IPC_STRUCT_TRAITS_BEGIN(struct_name)
 #define IPC_STRUCT_MEMBER(type, name) IPC_STRUCT_TRAITS_MEMBER(name)
@@ skipping 11 matching lines @@
 #define IPC_STRUCT_TRAITS_END() }
 
 #undef IPC_ENUM_TRAITS
 #define IPC_ENUM_TRAITS(enum_name) \
   void ParamTraits<enum_name>::Write(Message* m, const param_type& p) { \
     m->WriteInt(static_cast<int>(p)); \
   }
 
 #endif  // IPC_PARAM_TRAITS_WRITE_MACROS_H_