Change __defineGetter__ and __defineSetter__ to respect non-configurable....

test/mjsunit/regress/regress-1240.js

Index: test/mjsunit/regress/regress-1240.js
===================================================================
--- test/mjsunit/regress/regress-1240.js	(revision 0)
+++ test/mjsunit/regress/regress-1240.js	(revision 0)
@@ -0,0 +1,43 @@
+// Copyright 2011 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This regression tests that we are not allowed to overwrite an existing
+// non-configurable getter with a new getter. In addition, we should not
+// be able to change the configurable flag from false to true.
+
+var a = {};
+Object.defineProperty(a, 'b',
+                      { get: function () { return 42; }, configurable: false });
+try {
+  a.__defineGetter__('b', function _b(){ return 'foo'; });
+  assertUnreachable();
+} catch (e) {
+  assertTrue(/Cannot redefine property/.test(e));
+}
+assertEquals(42, a.b);
+var desc = Object.getOwnPropertyDescriptor(a, 'b');
+assertFalse(desc.configurable);