A MessageObject is a purely internal object to hold information about

src/objects.cc

 // 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 961 matching lines @@
       accumulator->Add("<ExternalUnsignedIntArray[%u]>",
                        ExternalUnsignedIntArray::cast(this)->length());
       break;
     case EXTERNAL_FLOAT_ARRAY_TYPE:
       accumulator->Add("<ExternalFloatArray[%u]>",
                        ExternalFloatArray::cast(this)->length());
       break;
     case SHARED_FUNCTION_INFO_TYPE:
       accumulator->Add("<SharedFunctionInfo>");
       break;
+    case JS_MESSAGE_OBJECT_TYPE:
+      accumulator->Add("<JSMessageObject>");
+      break;
 #define MAKE_STRUCT_CASE(NAME, Name, name) \
   case NAME##_TYPE:                        \
     accumulator->Put('<');                 \
     accumulator->Add(#Name);               \
     accumulator->Put('>');                 \
     break;
   STRUCT_LIST(MAKE_STRUCT_CASE)
 #undef MAKE_STRUCT_CASE
     case CODE_TYPE:
       accumulator->Add("<Code>");
@@ skipping 70 matching lines @@
       FixedArray::BodyDescriptor::IterateBody(this, object_size, v);
       break;
     case JS_OBJECT_TYPE:
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
     case JS_VALUE_TYPE:
     case JS_ARRAY_TYPE:
     case JS_REGEXP_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
     case JS_GLOBAL_OBJECT_TYPE:
     case JS_BUILTINS_OBJECT_TYPE:
+    case JS_MESSAGE_OBJECT_TYPE:
       JSObject::BodyDescriptor::IterateBody(this, object_size, v);
       break;
     case JS_FUNCTION_TYPE:
       reinterpret_cast<JSFunction*>(this)
           ->JSFunctionIterateBody(object_size, v);
       break;
     case ODDBALL_TYPE:
       Oddball::BodyDescriptor::IterateBody(this, v);
       break;
     case PROXY_TYPE:
@@ skipping 8785 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal