Bug 1074703 - [ValueSelector] Ensure window listener is removed on destroy

https://bugzilla.mozilla.org/show_bug.cgi?id=1074703
`var stub` is not necessary,
```
this.sinon.stub(app1.transitionController, 'destroy');
app1.destroy();
assert.ok(app1.transitionController.destroy.calledOnce);
```