Turn visitor_id into a byte field and free back one word in Map.

src/objects-inl.h

 // Copyright 2006-2008 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 2091 matching lines @@
 }
 
 
 void ExternalFloatArray::set(int index, float value) {
   ASSERT((index >= 0) && (index < this->length()));
   float* ptr = static_cast<float*>(external_pointer());
   ptr[index] = value;
 }
 
 
-INT_ACCESSORS(Map, visitor_id, kScavengerCallbackOffset)
+int Map::visitor_id() {
+  return READ_BYTE_FIELD(this, kVisitorIdOffset);
+}
+
+
+void Map::set_visitor_id(int id) {
+  ASSERT(0 <= id && id < 256);
+  WRITE_BYTE_FIELD(this, kVisitorIdOffset, static_cast<byte>(id));
+}
+
 
 int Map::instance_size() {
   return READ_BYTE_FIELD(this, kInstanceSizeOffset) << kPointerSizeLog2;
 }
 
 
 int Map::inobject_properties() {
   return READ_BYTE_FIELD(this, kInObjectPropertiesOffset);
 }
 
@@ skipping 1357 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_