Intent to ship: Change the effect of noopener window feature on other window features in window.open

[Anny Gakhokidze]

Relevant bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1419960

As of Firefox 63 I intend to make the noopener window feature not affect
whether
other window features are enabled.

Previously, window.open(url, "_blank", "noopener") would open a new window
with other window features, such as tab bar and back buttons, disabled.
With this change window.open(url, "_blank", "noopener") and
window.open(url, "_blank")
act exactly the same - they both open a new tab with all window features
*enabled*,
except that in first case opener is not set.

None of the other browsers have shipped it yet, but there is an existing
open bug
for Chrome https://bugs.chromium.org/p/chromium/issues/detail?id=596068.

- Anny