Implement correct checking for inherited readonliness on assignment.

test/mjsunit/override-read-only-property.js

 // Copyright 2009 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 20 matching lines @@
 //
 // However, for compatibility with WebKit/JSC, we allow the overriding
 // of read-only properties in prototype chains.
 
 function F() {};
 F.prototype = Number;
 
 var original_number_max = Number.MAX_VALUE;
 
 // Assignment to a property which does not exist on the object itself,
-// but is read-only in a prototype takes effect.
+// but is read-only in a prototype does not take effect.
 var f = new F();
 assertEquals(original_number_max, f.MAX_VALUE);
 f.MAX_VALUE = 42;
-assertEquals(42, f.MAX_VALUE);
+assertEquals(original_number_max, f.MAX_VALUE);
 
 // Assignment to a property which does not exist on the object itself,
-// but is read-only in a prototype takes effect.
+// but is read-only in a prototype does not take effect.
 f = new F();
 with (f) {
   MAX_VALUE = 42;
 }
-assertEquals(42, f.MAX_VALUE);
+assertEquals(original_number_max, f.MAX_VALUE);
 
 // Assignment to read-only property on the object itself is ignored.
 Number.MAX_VALUE = 42;
 assertEquals(original_number_max, Number.MAX_VALUE);
 
 // G should be read-only on the global object and the assignment is
 // ignored.
 (function G() {
   eval("G = 42;");
   assertTrue(typeof G === 'function');
 })();