Fix unexpected elements transition in JSON.parse

src/objects-inl.h

 // Copyright 2012 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 1487 matching lines @@
   if (!maybe->To(&map)) return maybe;
   set_map(map);
   initialize_elements();
 
   return this;
 }
 
 
 MaybeObject* JSObject::AllocateStorageForMap(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 =
       map->NumberOfOwnDescriptors() + map->unused_property_fields();
   int out_of_object = total_size - map->inobject_properties();
   if (out_of_object != properties()->length()) {
     FixedArray* new_properties;
     MaybeObject* maybe_properties = properties()->CopySize(out_of_object);
     if (!maybe_properties->To(&new_properties)) return maybe_properties;
     set_properties(new_properties);
@@ skipping 4671 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_