Change common_message_generator code block.

content/common/content_message_generator.cc

 // Copyright (c) 2010 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.
 
 // Get basic type definitions.
 #define IPC_MESSAGE_IMPL
 #include "content/common/common_param_traits.h"
 #include "content/common/content_message_generator.h"
 
 // Generate constructors.
 #include "ipc/struct_constructor_macros.h"
 #include "content/common/content_message_generator.h"
 
 // Generate destructors.
 #include "ipc/struct_destructor_macros.h"
 #include "content/common/content_message_generator.h"
 
-namespace IPC {
-
 // Generate param traits write methods.
 #include "ipc/param_traits_write_macros.h"
+namespace IPC {
 #include "content/common/content_message_generator.h"
+}  // namespace IPC
 
 // Generate param traits read methods.
 #include "ipc/param_traits_read_macros.h"
+namespace IPC {
 #include "content/common/content_message_generator.h"
+}  // namespace IPC
 
 // Generate param traits log methods.
 #include "ipc/param_traits_log_macros.h"
+namespace IPC {
 #include "content/common/content_message_generator.h"
+}  // namespace IPC
 
-}  // namespace IPC