European leaders head to Berlin Friday to seek assurances from US President Barack Obama on the course that Donald Trump might take, given the populist mogul’s pledges to shake up the world order. […] Ahead of the talks, Obama sounded a note of cautious optimism that Trump could change his position once he takes on the role as president. “There’s something about the solemn responsibilities of that office … that forces you to focus, that demands seriousness,” Obama said at a press conference following a meeting with his host Chancellor Angela Merkel. “And if you’re not serious about the job,...