Implement correct checking for inherited readonliness on assignment.

test/mjsunit/regress/regress-334.js

Index: test/mjsunit/regress/regress-334.js
diff --git a/test/mjsunit/regress/regress-334.js b/test/mjsunit/regress/regress-334.js
index 024fc9e856874c702eb7d8336416402db0ff888e..10c343d2dcdbf5a669fd27a636f8b47a6cf7e974 100644
--- a/test/mjsunit/regress/regress-334.js
+++ b/test/mjsunit/regress/regress-334.js
@@ -40,13 +40,14 @@ var object = {__proto__:{}};
 %SetProperty(object, "foo", func1, DONT_ENUM | DONT_DELETE);
 %SetProperty(object, "bar", func1, DONT_ENUM | READ_ONLY);
 %SetProperty(object, "baz", func1, DONT_DELETE | READ_ONLY);
-%SetProperty(object.__proto__, "bif", func1, DONT_ENUM | DONT_DELETE | READ_ONLY);
+%SetProperty(object.__proto__, "bif", func1, DONT_ENUM | DONT_DELETE);
 object.bif = func2;
 
 function enumerable(obj) {
   var res = [];
   for (var i in obj) {
     res.push(i);
+    print(i);
   }
   res.sort();
   return res;