[es6] Partially implement Reflect.preventExtensions.

test/mjsunit/harmony/reflect.js

 // Copyright 2015 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.
 
 // Flags: --harmony-reflect
 
 // TODO(neis): Test with proxies.
 
 
 
@@ skipping 238 matching lines @@
 (function testReflectIsExtensibleOnObject() {
   // This should be the last test as it modifies the objects irreversibly.
   for (let tgt of objects) {
     prepare(tgt);
     if (tgt instanceof Int32Array) continue;  // issue v8:4460
     assertTrue(Reflect.isExtensible(tgt));
     Object.preventExtensions(tgt);
     assertFalse(Reflect.isExtensible(tgt));
   }
 })();
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// Reflect.preventExtensions
+
+
+(function testReflectPreventExtensionsArity() {
+  assertEquals(1, Reflect.preventExtensions.length);
+})();
+
+
+(function testReflectPreventExtensionsOnNonObject() {
+  assertThrows(function() { Reflect.preventExtensions(); }, TypeError);
+  assertThrows(function() { Reflect.preventExtensions(42); }, TypeError);
+  assertThrows(function() { Reflect.preventExtensions(null); }, TypeError);
+})();
+
+
+// See reflect-prevent-extensions.js for further tests.
+
+// TODO(neis): Need proxies to test the situation where
+// [[preventExtensions]] returns false.