A percolating rebound at long last for Starbucks, with a side of a fresh concern. Starbucks investors have been waiting for clear signs of a turnaround under CEO Brian Niccol. The former Chipotle (CMG) CEO and top Yum! Brands (YUM) marketing mind brewed up several of those signs this week. On Wednesday, the company reported same-store sales growth in the US in the most recent quarter on the back of the new protein coffee, better food offerings, and quicker lines. Strong growth in China emerged, finally. ...