Bug 1100915 - [Usage][Refactoring] Use LazyLoader to load views. r=salva

>  Let's check for moving styles from the panel to the head (it suffices asserting parent is head)

I'm saying that, to pass the test for activation, it is enough by asserting the element is in the `<head>`, isn't it?:
```javascript
styleLinksIds.forEach((id) => {
  assert.equal(document.getElementById(id).parentNode, document.head);
});
```