A MessageObject is a purely internal object to hold information about

src/runtime.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 292 matching lines @@
   F(TraceEnter, 0, 1) \
   F(TraceExit, 1, 1) \
   F(Abort, 2, 1) \
   /* Logging */ \
   F(Log, 2, 1) \
   /* ES5 */ \
   F(LocalKeys, 1, 1) \
   /* Cache suport */ \
   F(GetFromCache, 2, 1) \
   \
+  /* Message objects */ \
+  F(NewMessageObject, 2, 1) \
+  F(MessageGetType, 1, 1) \
+  F(MessageGetArguments, 1, 1) \
+  F(MessageGetStartPosition, 1, 1) \
+  F(MessageGetScript, 1, 1) \
+  \
   /* Pseudo functions - handled as macros by parser */ \
   F(IS_VAR, 1, 1)
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 #define RUNTIME_FUNCTION_LIST_DEBUGGER_SUPPORT(F) \
   /* Debugger support*/ \
   F(DebugBreak, 0, 1) \
   F(SetDebugEventListener, 2, 1) \
   F(Break, 0, 1) \
   F(DebugGetPropertyDetails, 2, 1) \
@@ skipping 227 matching lines @@
                                                 int position);
 
   // Helper functions used stubs.
   static void PerformGC(Object* result);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_RUNTIME_H_