If a provider is enabled but not visible (eg, its worker is the only thing actually running) and it encounters an error, we need some way of surfacing that to the user so (a) the user knows it's not running and thus can't rely on it (eg, on incoming chats working) and (b) can take some remedial action, such as clicking a "restart provider" button or similar.

Just discussed with Boriss and here is the summary. If the provider has a worker and it fails to load for whatever reason: - Any content panel the provider has will display the error page when visible (iirc we already do this in some panels) - If the provider has a status button, we will badge it with an error indicator - We will add an error message in the provider listing in about:addons This conversation also brought up a 3rd state for providers. We currently have 2, enabled or disabled. If a user moves all the UI for the provider into the customization panel, the provider is effectively disabled though the worker would still be running. The user doesn't intend to disable the provider (via about:addons) as they may later want to move the icons out of customization back into use. This is something additional to think about. This is not a blocker for landing the other pieces in fx25. @Boriss, we probably need a mockup for what an error indicator on the status button should look like. Do we replace the button icon with an error icon, use a color, or put another image in the badge (which would be rather small)? or something else?

deprecation in fx51