[proxies] Use JSReceiver::GetKeys() for more purposes

test/mjsunit/harmony/proxies-for.js

Index: test/mjsunit/harmony/proxies-for.js
diff --git a/test/mjsunit/harmony/proxies-for.js b/test/mjsunit/harmony/proxies-for.js
index f0b36abbee71e0634154bc50fc56c7640dc2e874..92916f1c7e9ac7869914a13c1b93c788bd86bd98 100644
--- a/test/mjsunit/harmony/proxies-for.js
+++ b/test/mjsunit/harmony/proxies-for.js
@@ -142,7 +142,6 @@ TestForInThrow(new Proxy({}, {
 })();
 
 (function () {
-  var p = new Proxy({}, {getOwnPropertyNames:
-    function() { return [1, Symbol(), 2] }});
+  var p = new Proxy({}, {ownKeys: function() { return ["1", Symbol(), "2"] }});
   assertEquals(["1","2"], Object.getOwnPropertyNames(p));
 })();