Bug 1050684 - [Contacts-FTU] When FTU import Facebook Friends the next sync cycle must be scheduled

I would like to re-implement this like something like this:

init code:
```js
checkFacebookSynchronization(config);
```

```js
var checkFacebookSynchronization = function(config) {
  if (config && config.fbScheduleDone) {
    return;
  }

  var idleObserver = {
    time: 3,
    onidle: function() {
      // Your code calling navigator.removeIdleObserver(idleObserver); idleObserver = null;
    }
  };
  navigator.addIdleObserver(idleObserver);
}
```

I would like to have this change in order not to have this allocation fbScheduleIdleObserver. But this is just my opinion maybe @arcturus could give us his opinion here