Change common_message_generator code block.

content/common/content_message_generator.cc

Index: content/common/content_message_generator.cc
===================================================================
--- content/common/content_message_generator.cc	(revision 77874)
+++ content/common/content_message_generator.cc	(working copy)
@@ -15,18 +15,21 @@
 #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