Fix issue 720 making Object.defineProperty handle existing writable flags cor...

test/mjsunit/object-define-property.js

 // Copyright 2010 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 271 matching lines @@
 obj1.foobar = 1001;
 assertEquals(obj1.foobar, 1001);
 
 
 // Redefine with non configurable data property.
 Object.defineProperty(obj1, "foobar", dataNoConfigurable);
 desc = Object.getOwnPropertyDescriptor(obj1, "foobar");
 assertEquals(obj1.foobar, 2000);
 assertEquals(desc.value, 2000);
 assertFalse(desc.configurable);
-assertFalse(desc.writable);
+assertTrue(desc.writable);
 assertFalse(desc.enumerable);
 assertEquals(desc.get, undefined);
 assertEquals(desc.set, undefined);
 
 // Try redefine again - shold fail because configurable is now false.
 try {
   Object.defineProperty(obj1, "foobar", dataConfigurable);
   assertTrue(false);
 } catch (e) {
   assertTrue(/Cannot redefine property/.test(e));
 }
 
 // Try redefine again with accessor property - shold also fail.
 try {
   Object.defineProperty(obj1, "foobar", dataConfigurable);
   assertTrue(false);
 } catch (e) {
   assertTrue(/Cannot redefine property/.test(e));
 }
 
 
 // Redifine with the same descriptor - should succeed (step 6).
 Object.defineProperty(obj1, "foobar", dataNoConfigurable);
 desc = Object.getOwnPropertyDescriptor(obj1, "foobar");
 assertEquals(obj1.foobar, 2000);
 assertEquals(desc.value, 2000);
 assertFalse(desc.configurable);
-assertFalse(desc.writable);
+assertTrue(desc.writable);
 assertFalse(desc.enumerable);
 assertEquals(desc.get, undefined);
 assertEquals(desc.set, undefined);
 
 
 // New object
 var obj2 = {};
 
 // Make accessor - redefine to data
 Object.defineProperty(obj2, "foo", accessorConfigurable);
@@ skipping 376 matching lines @@
 
 // Make sure we can redefine with +0.
 Object.defineProperty(obj5, 'pluszero', descPlusZero);
 
 try {
   Object.defineProperty(obj5, 'pluszero', descMinusZero);
   assertUnreachable();
 } catch (e) {
   assertTrue(/Cannot redefine property/.test(e));
 }