Confusion on changing data property callback attributes

test/mjsunit/regress/regress-3334.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function foo(){}
+Object.defineProperty(foo, "prototype", { value: 2 });
+assertEquals(2, foo.prototype);
+
+function bar(){}
+Object.defineProperty(bar, "prototype", { value: 2, writable: false });
+assertEquals(2, bar.prototype);
+assertThrows(function() { "use strict"; bar.prototype = 10; }, TypeError);
+assertEquals(false, Object.getOwnPropertyDescriptor(bar,"prototype").writable);