[keys] fixing nested JSProxy for-in enumeration

test/mjsunit/es6/proxies-keys.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.
 
 var target = {
   target: 1
 };
 target.__proto__ = {
   target_proto: 2
 };
@@ skipping 19 matching lines @@
 assertEquals([], Object.keys(proxy));
 
 // Throwing shouldn't crash.
 handler.getOwnPropertyDescriptor = function() { throw new Number(1); };
 assertThrows("Object.keys(proxy)", Number);
 
 // Fall through to target if there is no trap.
 handler.ownKeys = undefined;
 assertEquals(["target"], Object.keys(proxy));
 assertEquals(["target"], Object.keys(target));
+
+var proxy2 = new Proxy(proxy, {});
+assertEquals(["target"], Object.keys(proxy2));
+
+
+(function testForSymbols() {
+  var symbol = Symbol();
+  var p = new Proxy({}, {ownKeys() { return ["1", symbol, "2"] }});
+  assertEquals(["1","2"], Object.getOwnPropertyNames(p));
+  assertEquals([symbol], Object.getOwnPropertySymbols(p));
+})();