emberjs/ember.js — pull request #3755 by hjdivad (2013-11-17 22:17:59+00:00)
Title: [FEATURE propertyBraceExpansion] Brace-expansion only in declarative form.

For performance reasons, property brace expansion is now only supported in declarative form. This is very unlikely to affect any users.

So the following works:
```js
var obj = { name: 'Edmure Tully', title: 'Lord Paramount of the Trident' };
Ember.mixin(obj, {
tridentObserver: function () {
}.observes('{name,title}')
});
```

While the following does not:
```js
var obj = { name: 'Edmure Tully', title: 'Lord Paramount of the Trident' };
Ember.addObserver(obj, '{name,title}', function () {});
```