[es6] Implement Reflect.enumerate.

test/mjsunit/harmony/reflect-enumerate-opt.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-proxies --allow-natives-syntax
+// This is adapted from mjsunit/for-in-opt.js.
+
+// Flags: --harmony-proxies --harmony-reflect --allow-natives-syntax
+
 
 "use strict";
 
-// Test non-JSObject receiver.
 function f(o) {
   var result = [];
-  for (var i in o) {
+  for (var i of Reflect.enumerate(Object(o))) {
     result.push(i);
   }
   return result;
 }
 
 assertEquals(["0"], f("a"));
 assertEquals(["0"], f("a"));
 %OptimizeFunctionOnNextCall(f);
 assertEquals(["0","1","2"], f("bla"));
 
@@ skipping 21 matching lines @@
     return {value: 10, configurable: true, writable: false, enumerable: true};
   }
 };
 
 
 var proxy = Proxy.create(handler);
 var o = {__proto__: proxy};
 
 function f2(o) {
   var result = [];
-  for (var i in o) {
+  for (var i of Reflect.enumerate(o)) {
     result.push(i);
   }
   return result;
 }
 
 function check_f2() {
   assertEquals(keys, f2(o));
   assertEquals(keys, has_keys);
   has_keys.length = 0;
 }
 
 check_f2();
 check_f2();
 // Test lazy deopt after GetPropertyNamesFast
 %OptimizeFunctionOnNextCall(f2);
 deopt_enum = true;
 check_f2();
 // Test lazy deopt after FILTER_KEY
 %OptimizeFunctionOnNextCall(f2);
 deopt_has = true;
 check_f2();
-
-function f3(o) {
-  for (var i in o) {
-  }
-}
-
-f3({__proto__:{x:1}});
-f3({__proto__:{x:1}});
-%OptimizeFunctionOnNextCall(f3);
-f3(undefined);
-f3(null);