Merged r14732, r14746, r14757 into 3.18 branch.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 29474b99fd5901cd4e8e9e27fb21a95e84edfd6a..09c07f977e8aa8dbf0d45535d96e8372ebf27575 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1514,9 +1514,19 @@ MaybeObject* JSObject::ResetElements() {
 
 MaybeObject* JSObject::TransitionToMap(Map* map) {
   ASSERT(this->map()->inobject_properties() == map->inobject_properties());
-  ElementsKind expected_kind = this->map()->elements_kind();
-  if (map->elements_kind() != expected_kind) {
-    MaybeObject* maybe_map = map->AsElementsKind(expected_kind);
+  ElementsKind obj_kind = this->map()->elements_kind();
+  ElementsKind map_kind = map->elements_kind();
+  if (map_kind != obj_kind) {
+    ElementsKind to_kind = map_kind;
+    if (IsMoreGeneralElementsKindTransition(map_kind, obj_kind) ||
+        IsDictionaryElementsKind(obj_kind)) {
+      to_kind = obj_kind;
+    }
+    MaybeObject* maybe_obj =
+        IsDictionaryElementsKind(to_kind) ? NormalizeElements()
+                                          : TransitionElementsKind(to_kind);
+    if (maybe_obj->IsFailure()) return maybe_obj;
+    MaybeObject* maybe_map = map->AsElementsKind(to_kind);
     if (!maybe_map->To(&map)) return maybe_map;
   }
   int total_size =