US President Donald Trump wore a face mask in public for the first time Saturday, finally yielding to intense pressure to set a public health example as the coronavirus rampages across America. Trump had on a dark mask featuring the presidential seal as he walked through the corridors of Walter Reed military hospital outside Washington to meet with wounded veterans. Trump strode past reporters and did not stop to speak to them about what had become a hotly anticipated moment — would he have a change of heart on a practice recommended by the government’s own medical experts, even as