[es6] Partially implement Reflect.preventExtensions.

test/mjsunit/harmony/reflect.js

Index: test/mjsunit/harmony/reflect.js
diff --git a/test/mjsunit/harmony/reflect.js b/test/mjsunit/harmony/reflect.js
index fc52c93d197c598978064b710f1e57648a44c691..e23c927733f203fa9a258a5dbbf0f69049097411 100644
--- a/test/mjsunit/harmony/reflect.js
+++ b/test/mjsunit/harmony/reflect.js
@@ -256,3 +256,26 @@ function prepare(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.