Moving prototype transitions into the header of the transition array.

src/transitions-inl.h

Index: src/transitions-inl.h
diff --git a/src/transitions-inl.h b/src/transitions-inl.h
index 9061883a270e7b3745d380de592c20b547181f03..a24bdfc8aaa4bcf67937abdcdefc48cf25ddf2cb 100644
--- a/src/transitions-inl.h
+++ b/src/transitions-inl.h
@@ -82,6 +82,42 @@ void TransitionArray::set_elements_transition(Map* transition_map,
 }
 
 
+bool TransitionArray::HasPrototypeTransitions() {
+  Object* prototype_transitions = get(kPrototypeTransitionsIndex);
+  return prototype_transitions != Smi::FromInt(0);
+}
+
+
+FixedArray* TransitionArray::prototype_transitions() {
+  Object* prototype_transitions = get(kPrototypeTransitionsIndex);
+  return FixedArray::cast(prototype_transitions);
+}
+
+
+HeapObject* TransitionArray::unchecked_prototype_transitions() {
+  Object* prototype_transitions = get(kPrototypeTransitionsIndex);
+  if (prototype_transitions == Smi::FromInt(0)) return NULL;
+  return reinterpret_cast<HeapObject*>(prototype_transitions);
+}
+
+
+void TransitionArray::set_prototype_transitions(FixedArray* transitions,
+                                                WriteBarrierMode mode) {
+  ASSERT(this != NULL);
+  ASSERT(transitions->IsFixedArray());
+  Heap* heap = GetHeap();
+  WRITE_FIELD(this, kPrototypeTransitionsOffset, transitions);
+  CONDITIONAL_WRITE_BARRIER(
+      heap, this, kPrototypeTransitionsOffset, transitions, mode);
+}
+
+
+Object** TransitionArray::GetPrototypeTransitionsSlot() {
+  return HeapObject::RawField(reinterpret_cast<HeapObject*>(this),
+                              kPrototypeTransitionsOffset);
+}
+
+
 Object** TransitionArray::GetKeySlot(int transition_number) {
   ASSERT(transition_number < number_of_transitions());
   return HeapObject::RawField(