Allow setting accessor infos over read-only but configurable properties.

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 <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 6328 matching lines @@
   // Ignore accessors on typed arrays.
   if (it.IsElement() && (object->HasFixedTypedArrayElements() ||
                          object->HasExternalArrayElements())) {
     return it.factory()->undefined_value();
   }
 
   CHECK(GetPropertyAttributes(&it).IsJust());
 
   // ES5 forbids turning a property into an accessor if it's not
   // configurable. See 8.6.1 (Table 5).
-  if (it.IsFound() && (it.IsReadOnly() || !it.IsConfigurable())) {
+  if (it.IsFound() && !it.IsConfigurable()) {
     return it.factory()->undefined_value();
   }
 
   it.TransitionToAccessorPair(info, info->property_attributes());
 
   return object;
 }
 
 
 MaybeHandle<Object> JSObject::GetAccessor(Handle<JSObject> object,
@@ skipping 9578 matching lines @@
                                             Handle<Object> new_value) {
   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