In bug 1352814, we added a hack to prevent the RDM container URL from being logged to session history, but it's not the nicest approach (we send some bogus data to wedge the session history listener). There already exist `disablehistory` / `disableglobalhistory` attributes for <xul:browser>, which seem like a better appoach. However, we are currently creating a tab for this case via `addTab` and this code path creates the <xul:browser>, so we'd need to expose an option to disable history in the `addTab` API.