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

chrome/common/nacl_messages_internal.h

Index: chrome/common/nacl_messages_internal.h
===================================================================
--- chrome/common/nacl_messages_internal.h	(revision 68536)
+++ chrome/common/nacl_messages_internal.h	(working copy)
@@ -6,25 +6,24 @@
 #include "chrome/common/nacl_types.h"
 #include "ipc/ipc_message_macros.h"
 
+#define IPC_MESSAGE_START NaClMsgStart
+
 //-----------------------------------------------------------------------------
 // NaClProcess messages
 // These are messages sent from the browser to the NaCl process.
-IPC_BEGIN_MESSAGES(NaClProcess)
-  // Tells the NaCl process to start.
-  IPC_MESSAGE_CONTROL1(NaClProcessMsg_Start,
-                       std::vector<nacl::FileDescriptor> /* sockets */)
+// Tells the NaCl process to start.
+IPC_MESSAGE_CONTROL1(NaClProcessMsg_Start,
+                     std::vector<nacl::FileDescriptor> /* sockets */)
 
-  // Tells the NaCl broker to launch a NaCl loader process.
-  IPC_MESSAGE_CONTROL1(NaClProcessMsg_LaunchLoaderThroughBroker,
-                       std::wstring /* channel ID for the loader */)
+// Tells the NaCl broker to launch a NaCl loader process.
+IPC_MESSAGE_CONTROL1(NaClProcessMsg_LaunchLoaderThroughBroker,
+                     std::wstring /* channel ID for the loader */)
 
-  // Notify the browser process that the loader was launched successfully.
-  IPC_MESSAGE_CONTROL2(NaClProcessMsg_LoaderLaunched,
-                       std::wstring,  /* channel ID for the loader */
-                       base::ProcessHandle /* loader process handle */)
+// Notify the browser process that the loader was launched successfully.
+IPC_MESSAGE_CONTROL2(NaClProcessMsg_LoaderLaunched,
+                     std::wstring,  /* channel ID for the loader */
+                     base::ProcessHandle /* loader process handle */)
 
-  // Notify the broker that all loader processes have been terminated and it
-  // should shutdown.
-  IPC_MESSAGE_CONTROL0(NaClProcessMsg_StopBroker)
-IPC_END_MESSAGES(NaClProcess)
-
+// Notify the broker that all loader processes have been terminated and it
+// should shutdown.
+IPC_MESSAGE_CONTROL0(NaClProcessMsg_StopBroker)