Fix another corner-case behavior of Object::SetSuperProperty.

src/objects.cc

 // Copyright 2013 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 <sstream>
 
@@ skipping 3747 matching lines @@
           return JSObject::SetPropertyWithFailedAccessCheck(&own_lookup, value,
                                                             should_throw);
         }
         break;
 
       case LookupIterator::INTEGER_INDEXED_EXOTIC:
         return RedefineIncompatibleProperty(it->isolate(), it->GetName(), value,
                                             should_throw);
 
       case LookupIterator::DATA: {
+        DCHECK(it->GetReceiver()->IsJSObject());
         PropertyDetails details = own_lookup.property_details();
-        if (details.IsConfigurable() || !details.IsReadOnly()) {
-          return JSObject::DefineOwnPropertyIgnoreAttributes(
-              &own_lookup, value, details.attributes(), should_throw);
+        if (details.IsReadOnly()) {
+          return WriteToReadOnlyProperty(&own_lookup, value, should_throw);
         }
-        return WriteToReadOnlyProperty(&own_lookup, value, should_throw);
+        if (!JSObject::IsExtensible(

[rossberg, 2015/11/03 10:55:11]

I don't think this check is correct. Extensibility doesn't matter if the
property already exists.

+                Handle<JSObject>::cast(it->GetReceiver()))) {
+          RETURN_FAILURE(it->isolate(), should_throw,
+                         NewTypeError(MessageTemplate::kObjectNotExtensible,
+                                      it->GetName()));
+        }
+        return JSObject::DefineOwnPropertyIgnoreAttributes(
+            &own_lookup, value, details.attributes(), should_throw);
       }
 
       case LookupIterator::ACCESSOR: {
         return RedefineIncompatibleProperty(it->isolate(), it->GetName(), value,
                                             should_throw);
       }
 
       case LookupIterator::INTERCEPTOR:
       case LookupIterator::JSPROXY: {
         bool found = false;
@@ skipping 14225 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8