Starbucks Corp on Tuesday said it is now offering its sales-boosting Mobile Order & Pay service in all of its more than 7,400 U.S. company-operated shops, completing its nationwide roll-out about three months ahead of schedule. Mobile Order & Pay is a feature on the Starbucks app, which the company says has 16 million active users on Apple and Android devices in the United States. Adam Brotman, Starbucks’ chief digital officer, said the coffee chain refined a variety of features before the expansion.