In my Firefox OS simulator, navigator.globalization.getLocaleName() passes the locale value directly to the successCallback. According to the documentation the successCallback should receive an object with the locale on the value property and on my android phone it works like this.
So is this a bug in the Firefox OS Simulator or a Cordova Bug? I'm using PhoneGap 5.3.9 with Cordova 5.4.1
That's it - firefoxos implementation bug.
Please file an issue to the Apache Cordova Jira issue tracker.