Change common_message_generator code block.

ipc/param_traits_read_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_READ_MACROS_H_
 #define IPC_PARAM_TRAITS_READ_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 18 matching lines @@
       Read(const Message* m, void** iter, param_type* p) { \
     int type; \
     if (!m->ReadInt(iter, &type)) \
       return false; \
     *p = static_cast<param_type>(type); \
     return true; \
   }
 
 #endif  // IPC_PARAM_TRAITS_READ_MACROS_H_