Bug 1009530 - [User Story] Visual to indicate when in edit mode

https://bugzilla.mozilla.org/show_bug.cgi?id=1009530

At the time it made more sense because the grid logic used to not be a component. Now that it's a component with it's own scoped stylesheet, we should probably remove that and allow apps to handle it how they'd like to. There's just a lot of moving pieces and a mountain of engineering debt :)