Boku requires a wait-to-finish view which polls for the transaction. Other providers are already further ahead in the overall so they need a success view that simply calls mozPaymentProvider.paymentSuccess() this could possibly be the same view as wait-to-finish as we know the provider there so we can easily make some changes. THere'll be another bug for the webpay side of this (e.g. we'll need to ensure webpay serves the right thing so the app can take over).
Following discussion with Kumar we've worked out a better approach to this. Will open new bugs for each provider implementation.