SHANGHAI, Dec 31 (Reuters) - China’s onshore spot yuan finished its domestic trading session at 6.5398 per dollar on Thursday, strengthening 6.5% against the greenback this year. If the spot price finishes the late-night session at the domestic closing level, it will book its first annual gain in three years thanks to a weaker dollar, a widening yield gap between China and the United States, and China’s coronavirus containment efforts. (Reporting by Shanghai and Beijing Newsroom; Editing by Hugh Lawson)