Fix FastAssign for self-assignment

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 2044 matching lines @@
       if (!it.IsFound()) continue;
       DCHECK(it.state() == LookupIterator::DATA ||
              it.state() == LookupIterator::ACCESSOR);
       if (!it.IsEnumerable()) continue;
       ASSIGN_RETURN_ON_EXCEPTION_VALUE(
           isolate, prop_value, Object::GetProperty(&it), Nothing<bool>());
     }
 
     if (use_set) {
       LookupIterator it(target, next_key, target);
-      bool call_to_js = it.IsFound() && it.state() != LookupIterator::DATA;
       Maybe<bool> result = Object::SetProperty(
           &it, prop_value, STRICT, Object::CERTAINLY_NOT_STORE_FROM_KEYED);
       if (result.IsNothing()) return result;
-      if (stable && call_to_js) stable = from->map() == *map;
+      if (stable) stable = from->map() == *map;
     } else {
       if (excluded_properties != nullptr &&
           HasExcludedProperty(excluded_properties, next_key)) {
         continue;
       }
 
       // 4a ii 2. Perform ? CreateDataProperty(target, nextKey, propValue).
       bool success;
       LookupIterator it = LookupIterator::PropertyOrElement(
           isolate, target, next_key, &success, LookupIterator::OWN);
@@ skipping 18584 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8