Key TakeawaysStarbucks on Tuesday tapped Chipotle CEO Brian Niccol to lead the company as the world's largest coffeehouse chain seeks to regain its footing.During Niccol's tenure at Chipotle, the restaurant steadily expanded its footprint and grew sales at a rate well ahead of most competitors.At Starbucks, Niccols will have to address a slowdown in China as competition grows more intense in the company's second-largest global market, slumping U.S. sales and demands from activist investors that have grown l ...