Chrome window has one browser element only in GeckoView. So even if
browser (Fenix etc) shows tabs, it is window.
When creating chrome window, we have to call Java code via
`nsIBrowserDOMWindow.createContentWindow` or
`nsIBrowserDOMWindow.createContentWindowInFrame`. So if we open
`geckoview.xhtml` directly, `geckoview.xhtml` throws an exception due to
missing initializing parameters.
Although `test_notification_serviceworker_openWindow.html` modifies
`browser.link.open_newwindow` preference, some values won't work since
`OpenWindowWithRemoteTab` is used to create browser and window in
`ContentParent::CommonCreateWindow`.
`OpenWindowWithRemoteTab` opens geckoview.xhtml directly, so it doesn't
work on GeckoView.
I would like to avoid this call and OpenWindowWithRemoteTab should
return an error in GeckoView immediately.
Differential Revision: https://phabricator.services.mozilla.com/D231055
e80df40a19