We should delete the isCustomNetwork state, and replace the network controller network state with networkStatus state.

The new state would be set to an enum representing the current status of the network network that is currently active (either "loading" or "active", unless someone thinks of a better alternative than "active"). This could be called networkStatus. This preserves the "loading" state.

The provider config state can be used in place of the isCustomNetwork property.

This is part of a larger effort to normalize the API of both network controllers, to make them easier to merge.

See here for related work on the extension: MetaMask/metamask-extension#16946