Bug 1102171 - [Usage][Refactoring] ViewManager.loadPanel should cleanup panels DOM once scripts/links are activated. r=salva

Continue with selecition by `href`. You're right otherwise seems a little bit weird.

As for the speed of `head > link` vs `getElementById`, although `head > link` involves a little bit more time due to the extra length of the rule, I think it's negligible. Let's continue this way.