BEIJING — President Trump and his Chinese counterpart, Xi Jinping, were all smiles and full of public praise for each other at the start of their much-anticipated summit meeting here Thursday. A very different story began to emerge behind closed doors after Xi continually pressed the issue of Taiwan , the self-governing, democratic island that China claims as its own. The mid-morning sitdown ran long — about 40 minutes over its scheduled time. Trump was notably quieter at the leaders’ next stop