[runtime] Fancify KeyAccumulator

test/mjsunit/third_party/object-keys/object-keys.js

 // Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // 1. Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 assertEquals(Object.keys("foo"), ["0", "1", "2"]);
 assertThrows(function () { Object.keys(null) }, TypeError);
 assertThrows(function () { Object.keys(undefined) }, TypeError);
 
 assertEquals(Object.keys({}), []);
 assertEquals(Object.keys({a:null}), ['a']);
 assertEquals(Object.keys({a:null, b:null}), ['a', 'b']);
 assertEquals(Object.keys({b:null, a:null}), ['b', 'a']);
 assertEquals(Object.keys([]), []);
 assertEquals(Object.keys([null]), ['0']);
+assertEquals(Object.keys([undefined]), ['0']);
 assertEquals(Object.keys([null,null]), ['0', '1']);
 assertEquals(Object.keys([null,null,,,,null]), ['0', '1', '5']);
 assertEquals(Object.keys({__proto__:{a:null}}), []);
 assertEquals(Object.keys({__proto__:[1,2,3]}), []);
 var x = [];
 x.__proto__ = [1, 2, 3];
 assertEquals(Object.keys(x), []);
 assertEquals(Object.keys(function () {}), []);
 
 assertEquals('string', typeof(Object.keys([1])[0]));
 
 function argsTest(a, b, c) {
   assertEquals(['0', '1', '2'], Object.keys(arguments));
 }
 
 argsTest(1, 2, 3);
 
 var literal = {a: 1, b: 2, c: 3};
 var keysBefore = Object.keys(literal);
 assertEquals(['a', 'b', 'c'], keysBefore);
 keysBefore[0] = 'x';
 var keysAfter = Object.keys(literal);
 assertEquals(['a', 'b', 'c'], keysAfter);
 assertEquals(['x', 'b', 'c'], keysBefore);
+
+
+var o = [1, 2, 3];
+assertEquals(['0', '1', '2'], Object.keys(o));
+Object.defineProperty(o, '0', {
+    enumerable: false,
+});
+assertEquals(['1', '2'], Object.keys(o));
+
+
+(function(){
+  assertEquals(['0', '1', '2'], Object.keys(arguments));
+  Object.defineProperty(arguments, '0', {
+      enumerable: false,
+  });
+  assertEquals(['1', '2'], Object.keys(arguments));
+})(0,1,2);
+
+
+(function(a, b){
+  assertEquals(['0', '1', '2'], Object.keys(arguments));
+  Object.defineProperty(arguments, '0', {
+      enumerable: false,
+  });
+  assertEquals(['1', '2'], Object.keys(arguments));
+})(0,1,2);
+
+var b = [];
+assertEquals(0, Object.keys(b).length);
+b[0] = undefined;
+assertEquals(1, Object.keys(b).length);