Desperate to save his own head in the fallout over the recorded police killing of Laquan McDonald, Mayor Rahm Emanuel reached for another. Another head, that is. This one belonged to Garry McCarthy, Chicago's superintendent of police, who just the other day said he'd never, ever quit. "I never quit on anything in my life," McCarthy told reporters late last week, after protesters closed Michigan Avenue on Black Friday, after the mayor hid out, lying low, letting McCarthy and Cook County State's Attorney Anita Alvarez take all the heat. "The mayor has made it very clear that he has my...