Handlify JSObject::SetPrototype method.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index ea347fd354bcb77a2c7240a3b3bcd275cf86a53a..fe054dad4b557ddd9a76606096338941c076cd22 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4285,6 +4285,7 @@ FixedArray* Map::GetPrototypeTransitions() {
 MaybeObject* Map::SetPrototypeTransitions(FixedArray* proto_transitions) {
   MaybeObject* allow_prototype = EnsureHasTransitionArray(this);
   if (allow_prototype->IsFailure()) return allow_prototype;
+  int old_number_of_transitions = NumberOfProtoTransitions();
 #ifdef DEBUG
   if (HasPrototypeTransitions()) {
     ASSERT(GetPrototypeTransitions() != proto_transitions);
@@ -4292,6 +4293,7 @@ MaybeObject* Map::SetPrototypeTransitions(FixedArray* proto_transitions) {
   }
 #endif
   transitions()->SetPrototypeTransitions(proto_transitions);
+  SetNumberOfProtoTransitions(old_number_of_transitions);
   return this;
 }