Remove the extensibility flag. Instead just rely on hidden_string as indication.

src/objects.h

 // Copyright 2012 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/builtins.h"
@@ skipping 229 matching lines @@
 
 
 // PropertyNormalizationMode is used to specify whether to keep
 // inobject properties when normalizing properties of a JSObject.
 enum PropertyNormalizationMode {
   CLEAR_INOBJECT_PROPERTIES,
   KEEP_INOBJECT_PROPERTIES
 };
 
 
-// Internal properties (e.g. the hidden properties dictionary) might
-// be added even though the receiver is non-extensible.
-enum ExtensibilityCheck {
-  PERFORM_EXTENSIBILITY_CHECK,
-  OMIT_EXTENSIBILITY_CHECK
-};
-
-
 // Indicates how aggressively the prototype should be optimized. FAST_PROTOTYPE
 // will give the fastest result by tailoring the map to the prototype, but that
 // will cause polymorphism with other objects. REGULAR_PROTOTYPE is to be used
 // (at least for now) when dynamically modifying the prototype chain of an
 // object using __proto__ or Object.setPrototypeOf.
 enum PrototypeOptimizationMode { REGULAR_PROTOTYPE, FAST_PROTOTYPE };
 
 
 // Indicates whether transitions can be added to a source map or not.
 enum TransitionFlag {
@@ skipping 1236 matching lines @@
 
   MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
       LookupIterator* it, Handle<Object> value, StrictMode strict_mode,
       StoreFromKeyed store_mode);
   MUST_USE_RESULT static MaybeHandle<Object> WriteToReadOnlyProperty(
       LookupIterator* it, Handle<Object> value, StrictMode strict_mode);
   MUST_USE_RESULT static MaybeHandle<Object> SetDataProperty(
       LookupIterator* it, Handle<Object> value);
   MUST_USE_RESULT static MaybeHandle<Object> AddDataProperty(
       LookupIterator* it, Handle<Object> value, PropertyAttributes attributes,
-      StrictMode strict_mode, StoreFromKeyed store_mode,
-      ExtensibilityCheck check);
+      StrictMode strict_mode, StoreFromKeyed store_mode);
   MUST_USE_RESULT static inline MaybeHandle<Object> GetPropertyOrElement(
       Handle<Object> object,
       Handle<Name> key);
   MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
       Isolate* isolate,
       Handle<Object> object,
       const char* key);
   MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
       Handle<Object> object,
       Handle<Name> key);
@@ skipping 627 matching lines @@
   enum ExecutableAccessorInfoHandling {
     DEFAULT_HANDLING,
     DONT_FORCE_FIELD
   };
 
   MUST_USE_RESULT static MaybeHandle<Object> SetOwnPropertyIgnoreAttributes(
       Handle<JSObject> object,
       Handle<Name> key,
       Handle<Object> value,
       PropertyAttributes attributes,
-      ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK,
       StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED,
       ExecutableAccessorInfoHandling handling = DEFAULT_HANDLING);
 
   static void AddProperty(Handle<JSObject> object, Handle<Name> key,
                           Handle<Object> value, PropertyAttributes attributes);
 
   // Extend the receiver with a single fast property appeared first in the
   // passed map. This also extends the property backing store if necessary.
   static void AllocateStorageForMap(Handle<JSObject> object, Handle<Map> map);
 
@@ skipping 9066 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_