`isInApp` is not the right name for this function, since even an app (for instance, twitter) can have a history. Also, we need to confirm with UX that this change is ok. For instance, if you are browsing a hosted app, and suddenly go offline, the cancel button will not try to take you back rather than closing the app. I'll have to double check, but I don't think that is what the spec says, so we should confirm with them.