(Reuters) - U.S. Open champion Dustin Johnson sleep-walked through his first four holes before snapping to attention to fashion a one-under-par 71 and remain tied for the lead after the second round at the RBC Canadian Open on Friday. Johnson, who shared the overnight lead with fellow American Luke List after an opening 66, had an early tee time. "I just got in some tough spots," said Johnson, who finished the day on seven-under 137 to share the halfway lead with List at Glen Abbey outside of Toronto. More...