Shares in King Digital Entertainment Plc fell as much as 16 percent in their Wednesday debut, underscoring investor concern about the company’s reliance on “Candy Crush Saga” and dampening hopes that its coming-out party could revive investor interest in the mobile gaming industry. Mobile game industry executives had looked to London-based King’s IPO, the largest by a gaming company since Zynga Inc went public in 2011, to help sweep aside skepticism over a notoriously fickle, volatile market.