Add map transition for observed objects

src/objects.cc

 // Copyright 2013 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 6653 matching lines @@
   if (insert_transition) {
     MaybeObject* added_elements = set_elements_transition_map(new_map);
     if (added_elements->IsFailure()) return added_elements;
     new_map->SetBackPointer(this);
   }
 
   return new_map;
 }
 
 
+MaybeObject* Map::CopyForObserved() {
+  ASSERT(!is_observed());
+
+  Map* new_map;
+  MaybeObject* maybe_new_map;
+  if (owns_descriptors()) {
+    maybe_new_map = CopyDropDescriptors();
+  } else {
+    maybe_new_map = Copy();
+  }
+  if (!maybe_new_map->To(&new_map)) return maybe_new_map;
+
+  TransitionArray* transitions;
+  MaybeObject* maybe_transitions = AddTransition(GetHeap()->observed_symbol(),
+                                                 new_map,
+                                                 FULL_TRANSITION);
+  if (!maybe_transitions->To(&transitions)) return maybe_transitions;
+  set_transitions(transitions);
+
+  new_map->set_is_observed(true);
+
+  if (owns_descriptors()) {
+    new_map->InitializeDescriptors(instance_descriptors());
+    set_owns_descriptors(false);
+  }
+
+  new_map->SetBackPointer(this);
+  return new_map;
+}
+
+
 MaybeObject* Map::CopyWithPreallocatedFieldDescriptors() {
   if (pre_allocated_property_fields() == 0) return CopyDropDescriptors();
 
   // If the map has pre-allocated properties always start out with a descriptor
   // array describing these properties.
   ASSERT(constructor()->IsJSFunction());
   JSFunction* ctor = JSFunction::cast(constructor());
   Map* map = ctor->initial_map();
   DescriptorArray* descriptors = map->instance_descriptors();
 
@@ skipping 9187 matching lines @@
 
 void PropertyCell::AddDependentCode(Handle<Code> code) {
   Handle<DependentCode> codes = DependentCode::Insert(
       Handle<DependentCode>(dependent_code()),
       DependentCode::kPropertyCellChangedGroup, code);
   if (*codes != dependent_code()) set_dependent_code(*codes);
 }
 
 
 } }  // namespace v8::internal