Allow Object.defineProperty to update value of an API accessor.

src/runtime.cc

 // 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 5211 matching lines @@
       !isolate->MayNamedAccess(js_object, name, v8::ACCESS_SET)) {
     return isolate->heap()->undefined_value();
   }
 
   LookupResult lookup(isolate);
   js_object->LocalLookupRealNamedProperty(*name, &lookup);
 
   // Special case for callback properties.
   if (lookup.IsPropertyCallbacks()) {
     Handle<Object> callback(lookup.GetCallbackObject(), isolate);
-    // To be compatible with Safari we do not change the value on API objects
-    // in Object.defineProperty(). Firefox disagrees here, and actually changes
-    // the value.
-    if (callback->IsAccessorInfo()) {
-      return isolate->heap()->undefined_value();
-    }
-    // Avoid redefining foreign callback as data property, just use the stored
+    // Avoid redefining callback as data property, just use the stored
     // setter to update the value instead.
     // TODO(mstarzinger): So far this only works if property attributes don't
     // change, this should be fixed once we cleanup the underlying code.
-    if (callback->IsForeign() && lookup.GetAttributes() == attr) {
+    if ((callback->IsForeign() || callback->IsAccessorInfo()) &&
+        lookup.GetAttributes() == attr) {
       Handle<Object> result_object;
       ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
           isolate, result_object,
           JSObject::SetPropertyWithCallback(js_object,
                                             callback,
                                             name,
                                             obj_value,
                                             handle(lookup.holder()),
                                             STRICT));
       return *result_object;
@@ skipping 9871 matching lines @@
   }
   return NULL;
 }
 
 
 const Runtime::Function* Runtime::FunctionForId(Runtime::FunctionId id) {
   return &(kIntrinsicFunctions[static_cast<int>(id)]);
 }
 
 } }  // namespace v8::internal