American ski queen Mikaela Shiffrin dominated a slalom in Austria on Thursday to become the first alpine skier to win 50 World Cup races in one discipline. Shiffrin claimed her third victory in as many days at Semmering’s Magic Mountain, following two giant slalom top spots, ahead of compatriot Paula Moltzan and German Lena Dürr. Shffrin now has 80 career top spots, just two shy of compatriot Lindsey Vonn’s women’s record 82 wins, and six off the overall record 86 achieved by former Swedish great Ingemar Stenmark. Shiffrin, 27, can attack Vonn’s record next week which features two slaloms in Z…