Ideally, formAttributeName would be a field on the prototype of each front,
but unfortunately, Firefox doesn't support ES Class's fields yet. So it is
put as an instance attribute instead.
This patch streamline the manually set actorID and the retrieval of actor ID
from root or target front's form into `getFront` helper method.
So that all the specific related to the lazy actor is now inside of this helper.
It also moves the special "this.manage(this)" to this helper.
We might be able to followup on this one and finally have only the root front
being self managed. But the initialize method makes it hard.
Note the special tweak made to devtools/client/responsive.html/manager.js
Hopefully this can be removed once the target classes are merged.
Depends on D15832
Differential Revision: https://phabricator.services.mozilla.com/D17615
--HG--
extra : moz-landing-system : lando
