Fix issue 965.

Review URL: http://codereview.chromium.org/5773002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5960 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/v8natives.js

@@ -615,7 +615,13 @@ function DefineOwnProperty(obj, p, desc, should_throw) {
     } else {
       flag |= READ_ONLY;
     }
-    %DefineOrRedefineDataProperty(obj, p, desc.getValue(), flag);
+    var value;  // Default value is undefined.
+    if (desc.hasValue()) {
+      value = desc.getValue();
+    } else if (!IS_UNDEFINED(current)) {
+      value = current.getValue();
+    }
+    %DefineOrRedefineDataProperty(obj, p, value, flag);
   } else {
     if (desc.hasGetter() && IS_FUNCTION(desc.getGet())) {
        %DefineOrRedefineAccessorProperty(obj, p, GETTER, desc.getGet(), flag);

test/mjsunit/object-define-property.js

@@ -866,4 +866,36 @@ assertFalse(desc.writable);
 assertFalse(desc.enumerable);
 assertFalse(desc.configurable);
 
+// See issue 968: http://code.google.com/p/v8/issues/detail?id=968
+var o = { x : 42 };
+Object.defineProperty(o, "x", { writable: false });
+assertEquals(42, o.x);
+o.x = 37;
+assertEquals(42, o.x);
+
+o = { x : 42 };
+Object.defineProperty(o, "x", {});
+assertEquals(42, o.x);
+o.x = 37;
+// Writability is preserved.
+assertEquals(37, o.x);
+
+var o = { };
+Object.defineProperty(o, "x", { writable: false });
+assertEquals(undefined, o.x);
+o.x = 37;
+assertEquals(undefined, o.x);
+
+o = { get x() { return 87; } };
+Object.defineProperty(o, "x", { writable: false });
+assertEquals(undefined, o.x);
+o.x = 37;
+assertEquals(undefined, o.x);
+
+// Ignore inherited properties.
+o = { __proto__ : { x : 87 } };
+Object.defineProperty(o, "x", { writable: false });
+assertEquals(undefined, o.x);
+o.x = 37;
+assertEquals(undefined, o.x);