Should you use `Ember.keys` instead `Object.keys`? The latter seems [not to be supported everywhere](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys), whereas `Ember.keys` [handles that](https://github.com/emberjs/ember.js/blob/v1.3.0/packages/ember-runtime/lib/core.js#L258-L268)