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

I still using this check because inside panel script/link doesn't have id, so it doesn't really matter where this node was added, the main thing it was activated, and check that we set ```href/src``` correctly. If we're able to _move_ these nodes instead in https://bugzilla.mozilla.org/show_bug.cgi?id=1102171 then I'll simplify this.