Follow jsc on not throwing when trying to add a property to a non-extensible object.

test/mjsunit/object-seal.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 57 matching lines @@
 
 // Make sure we are no longer extensible.
 assertFalse(Object.isExtensible(obj));
 assertTrue(Object.isSealed(obj));
 
 // We should not be frozen, since we are still able to
 // update values.
 assertFalse(Object.isFrozen(obj));
 
 // We should not allow new properties to be added.
-try {
-   obj.foo = 42;
-   assertUnreachable();
-} catch(e) {
-  assertTrue(/object is not extensible/.test(e));
-}
+obj.foo = 42;
+assertEquals(obj.foo, undefined);
 
 desc = Object.getOwnPropertyDescriptor(obj, 'x');
 assertTrue(desc.writable);
 assertFalse(desc.configurable);
 assertEquals(42, desc.value);
 
 desc = Object.getOwnPropertyDescriptor(obj, 'z');
 assertTrue(desc.writable);
 assertFalse(desc.configurable);
 assertEquals("foobar", desc.value);
@@ skipping 24 matching lines @@
 assertTrue(Object.isFrozen(obj2));
 assertFalse(Object.isExtensible(obj2));
 assertTrue(Object.isSealed(obj2));
 
 desc = Object.getOwnPropertyDescriptor(obj2, 'x');
 assertFalse(desc.configurable);
 assertEquals(undefined, desc.value);
 assertEquals(set, desc.set);
 assertEquals(get, desc.get);
 
-try {
-  obj2.foo = 42;
-  assertUnreachable();
-} catch(e) {
-  assertTrue(/object is not extensible/.test(e));
-}
-
+obj2.foo = 42;
+assertEquals(obj2.foo, undefined);
 
 // Test seal on arrays.
 var arr = new Array(42,43);
 
 desc = Object.getOwnPropertyDescriptor(arr, '0');
 assertTrue(desc.configurable);
 assertTrue(desc.writable);
 assertEquals(42, desc.value);
 
 desc = Object.getOwnPropertyDescriptor(arr, '1');
@@ skipping 45 matching lines @@
 var obj4 = {};
 Object.defineProperty(obj4, 'x', {configurable: true, writable: false});
 Object.defineProperty(obj4, 'y', {configurable: false, writable: false});
 Object.preventExtensions(obj4);
 
 assertFalse(Object.isSealed(obj4));
 
 // Make sure that Object.seal returns the sealed object.
 var obj4 = {}
 assertTrue(obj4 === Object.seal(obj4))