The other answers are outdated. The behavior of Chrome for window.open depends on where it is called from. See also this topic.
When window.open is called from a handler that was triggered though a user action (e.g. onclick event), it will behave similar as <a target="_blank">, which by default opens in a new tab. However if window.open is called elsewhere, Chrome ignores other arguments and always opens a new window with a non-editable address bar.
This looks like some kind of security measure, although the rationale behind it is not completely clear.