Open 2015: Dustin Johnson determined to forget his major misadventures

• American focuses on learning from Chambers Bay calamity
• ‘I try to look at them all as learning opportunities’Dustin Johnson is aware as anyone that he really should have won his first major by now, if not much at Whistling Straits in 2010 or Royal St George’s in 2011 then certainly at Chambers Bay last month when a 12-foot putt would have been enough to secure the US Open.“You know, I knew I needed to make birdie,” he said on Monday about his experience on the par-five 18th. �