From the moment Air Force One touches down in Beijing Wednesday, Taiwan officials will be scrutinizing U.S. President Donald Trump’s every word. On his first visit to China in nearly a decade, what Mr. Trump says – or doesn’t say – could greatly impact the future of the self-governing island, which Beijing claims as part of China. Chinese leader Xi Jinping has already stressed directly to Mr. Trump that Taiwan is the “most important issue” in U.S.-China relations. Indeed, one of the biggest questions looming over their visit is whether Mr. Trump will bend to pressure from Beijing to curtail American diplomatic or military support for Taiwan, breaking with decades of U.S. foreign policy. Other U.S. allies in the Pacific will be watching, too. The talks’ high stakes can be summed up in one word: trust.…