I cloned test262 es5-tests branch under test/script/external and ran "ant clean test262parallel". 

test/script/external/test262/test/suite/ch12/12.6/12.6.4/12.6.4-2.js fails with tip.

Copying the test content here for quick reference:

/**
 * @path ch12/12.6/12.6.4/12.6.4-2.js
 * @description The for-in Statement - the values of [[Enumerable]] attributes are not considered when determining if a property of a prototype object is shadowed by a previous object on the prototype chain
 */


function testcase() {
        var proto = {
            prop: "enumerableValue"
        };

        var ConstructFun = function () { };
        ConstructFun.prototype = proto;

        var child = new ConstructFun();

        Object.defineProperty(child, "prop", {
            value: "nonEnumerableValue",
            enumerable: false
        });

        var accessedProp = false;

        for (var p in child) {
            if (p === "prop") {
                accessedProp = true;
            }
        }
        return !accessedProp;
    }
runTestCase(testcase);