Why is there no Object.setPrototypeOf(...) in ECMAScript 5 standard?

Question

Apparently using __proto__ property is still the main way of manipulating prototype chains, even though this is not standards compliant and IE does not support it. Though you can also construct inheritance through the use of new constructor this seems like an unnecessary complication compared to __proto__ property or standards compliant Object.getPrototypeOf function.

Edit:

As stated in the answers, this method does exist now (ES6 standard). Be aware of the performance warning, though: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf

Answer 1

It is part of the ES6 harmony draft:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/setPrototypeOf

I am using it now in the latest release of Chrome.

var proto = {
    foo: 'bar'
};

var object = {};

Object.setPrototypeOf(object, proto);

console.assert(object.foo == 'bar');