Revert of [runtime] Do not use the enum-cache for non-prototype objects.

test/mjsunit/regress/regress-705-shadowed_properties.js

-// Copyright 2016 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.
-
-function allKeys(object) {
-  var keys = [];
-  for (var key in object) {
-    keys.push(key);
-  }
-  return keys;
-}
-
-var a = { a1: true, a2: true};
-var b = { b1: true, b2: true};
-a.__proto__ = b;
-
-assertEquals(['a1', 'a2', 'b1', 'b2'], allKeys(a));
-assertEquals(['b1', 'b2'], allKeys(b));
-
-// Adding a non-enumerable property to either a or b shouldn't change
-// the result.
-var propertyDescriptor = {
-  enumerable: false,
-  configurable: true,
-  writable: true,
-  value: true
-};
-
-Object.defineProperty(a, 'a3', propertyDescriptor);
-assertEquals(['a1', 'a2', 'b1', 'b2'], allKeys(a));
-assertEquals(['b1', 'b2'], allKeys(b));
-
-Object.defineProperty(b, 'b3', propertyDescriptor);
-assertEquals(['a1', 'a2', 'b1', 'b2'], allKeys(a));
-assertEquals(['b1', 'b2'], allKeys(b));
-
-// A non-enumerable property shadows an enumerable version on the prototype
-// chain.
-b['a3'] = true;
-assertEquals(['a1', 'a2', 'b1', 'b2'], allKeys(a));
-assertEquals(['b1', 'b2', 'a3'], allKeys(b));
-
-// Try the same with indexed-properties.
-var aIndex  = {0:true, 1:true};
-var bIndex = {10:true, 11:true};
-aIndex.__proto__= bIndex;
-assertEquals(['0', '1', '10', '11'], allKeys(aIndex));
-assertEquals(['10', '11'], allKeys(bIndex));
-
-Object.defineProperty(aIndex, 2, propertyDescriptor);
-Object.defineProperty(bIndex, 12, propertyDescriptor);
-assertEquals(['0', '1', '10', '11'], allKeys(aIndex));
-assertEquals(['10', '11'], allKeys(bIndex));
-
-bIndex[2] = 2;
-assertEquals(['0', '1', '10', '11'], allKeys(aIndex));
-assertEquals(['2', '10', '11'], allKeys(bIndex));