Nike Inc. shares tumbled after the retailer gave a surprisingly gloomy outlook for the year ahead, complicating Chief Executive Officer Elliott Hill’s efforts to turn around the business. Revenue is expected to decline 2% to 4% in the current quarter and will be down in the low single-digits for the rest of the calendar year, management told investors on an earnings call Tuesday evening. Analysts surveyed by Bloomberg had been looking for 2% sales growth this quarter and bigger gains as the year...