Simplify the magic required to create IPC message headers a bit.

ipc/ipc_sync_channel_unittest.cc

Index: ipc/ipc_sync_channel_unittest.cc
===================================================================
--- ipc/ipc_sync_channel_unittest.cc	(revision 68536)
+++ ipc/ipc_sync_channel_unittest.cc	(working copy)
@@ -22,14 +22,9 @@
 #include "ipc/ipc_sync_message_filter.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#define IPC_MESSAGE_IMPL
+#include "ipc/ipc_sync_message_unittest.h"
 
-#define MESSAGES_INTERNAL_FILE "ipc/ipc_sync_message_unittest.h"
-#include "ipc/ipc_message_macros.h"
-
-// Definition of IPC Messages used for this test.
-#define MESSAGES_INTERNAL_IMPL_FILE "ipc/ipc_sync_message_unittest.h"
-#include "ipc/ipc_message_impl_macros.h"
-
 using namespace IPC;
 using base::WaitableEvent;