Reimplement SetProperty using the LookupIterator

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index b01c49d2b4fcb66b8f949b622e1c9ea1d1c0d2f5..d348dc07bacccd4ece13ec577eaa988a5ee33961 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -2079,23 +2079,12 @@ bool JSObject::HasFastProperties() {
 }
 
 
-bool JSObject::TooManyFastProperties(StoreFromKeyed store_mode) {
-  // Allow extra fast properties if the object has more than
-  // kFastPropertiesSoftLimit in-object properties. When this is the case, it is
-  // very unlikely that the object is being used as a dictionary and there is a
-  // good chance that allowing more map transitions will be worth it.
-  Map* map = this->map();
-  if (map->unused_property_fields() != 0) return false;
-
-  int inobject = map->inobject_properties();
-
-  int limit;
-  if (store_mode == CERTAINLY_NOT_STORE_FROM_KEYED) {
-    limit = Max(inobject, kMaxFastProperties);
-  } else {
-    limit = Max(inobject, kFastPropertiesSoftLimit);
-  }
-  return properties()->length() > limit;
+bool Map::TooManyFastProperties(StoreFromKeyed store_mode) {
+  if (unused_property_fields() != 0) return false;
+  int minimum = store_mode == CERTAINLY_NOT_STORE_FROM_KEYED ? 128 : 12;
+  int limit = Max(minimum, inobject_properties());
+  int external = NumberOfFields() - inobject_properties();
+  return external > limit;
 }