Make IsGenericDescriptor spec-conformant.

src/v8natives.js

 // Copyright 2011 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 355 matching lines @@
 
 // ES5 8.10.2.
 function IsDataDescriptor(desc) {
   if (IS_UNDEFINED(desc)) return false;
   return desc.hasValue() || desc.hasWritable();
 }
 
 
 // ES5 8.10.3.
 function IsGenericDescriptor(desc) {
+  if (IS_UNDEFINED(desc)) return false;
   return !(IsAccessorDescriptor(desc) || IsDataDescriptor(desc));
 }
 
 
 function IsInconsistentDescriptor(desc) {
   return IsAccessorDescriptor(desc) && IsDataDescriptor(desc);
 }
 
 
 // ES5 8.10.4
@@ skipping 1220 matching lines @@
 
 function SetUpFunction() {
   %CheckIsBootstrapping();
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetUpFunction();