UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36

Steps to reproduce the problem:
1. Enter a website that has iframes in it:
https://www.w3schools.com/html/html_iframe.asp

2. Open developer tools, go to console, and run the following:
resultFromObj = Object.getOwnPropertyNames(window)
resultFromFor = []
for (var name in window) {
    resultFromFor.push(name);
}

3. Inspect the results of the commands, using the following commands:
console.log(resultFromObj.indexOf("0") != -1, resultFromObj.indexOf("1") != -1) // Prints false false
console.log(resultFromFor.indexOf("0") != -1, resultFromFor.indexOf("1") != -1) // Prints false false

What is the expected behavior?
Both console.log lines, should return 'true true', which implies that the frames that exist on the page should exist in the resulting arrays.

What went wrong?
Both the for..in loop that was ran, and the Object.getOwnPropertyNames function that was called, did not return the frames that reside inside the window object.
The specific website I've mentioned above, has 2 frames, hence the check for the existance of "0" and "1" in the resulting arrays.
I am reporting this behavior because it does not conform to the defined specifications, which state that both of those enumeration methods, should use [[OwnPropertyKeys]] to get the keys of the object, which should indeed include the frames of the window in it's result.

The specification for [[OwnPropertyKeys]], from which we can tell that the frames should be there is located here:
https://html.spec.whatwg.org/multipage/browsers.html#windowproxy-ownpropertykeys

The specification for the Object.getOwnPropertyNames can be seen here:
https://tc39.github.io/ecma262/#sec-object.getownpropertynames
and subsequently here:
https://tc39.github.io/ecma262/#sec-getownpropertykeys

The specification for the for..in loop is located here:
https://tc39.github.io/ecma262/#sec-enumerate-object-properties

Did this work before? N/A 

Chrome version: 55.0.2883.87  Channel: stable
OS Version: Linux michx 4.9.9-1-ARCH #1 SMP PREEMPT Thu Feb 9 19:07:09 CET 2017 x86_64 GNU/Linux
Flash Version: Shockwave Flash 24.0 r0

Also, from my tests, Mozilla Firefox is already up to spec on this matter, for quite some time.