ABU DHABI — Five leading contenders for football’s Asian Cup, which starts in the United Arab Emirates on Saturday: 1. Australia The Socceroos won the biggest title in their history at the last Asian Cup in 2015, where they edged South Korea after extra time to win a thrilling final in Sydney. It provided further vindication for their switch from Oceania to the Asian confederation in 2006, since when they have never failed to qualify for the World Cup. However, Australia’s star has dimmed in recent times, and after reaching Russia 2018 via the play-offs they exited without a win after scoring only twice in their three group games. New coach Graham Arnold must fill the void left by retired record scorer Tim Cahill, and get the goals flowing again, if the Socceroos are to keep the trophy in Australian hands. 2. Iran Asia’s top-ranked team won credit at last year’s World Cup, where they were edged 1-0 by Spain and finished 1-1 against Cristiano Ronaldo’s Portugal, before exiting at the group stage. However, they will want to go home with more than just praise at the Asian Cup, a tournament where success has eluded them since their run of…