Just when you'd warmed to the idea of three navigation buttons on HTC's One lineup, the company went back and re-added a fourth button to the row -- in mainland China, anyway. To follow the debut of its Desire (aka Dragon) lineup, HTC has introduced a One S variant that it designed in collaboration with Sina Weibo, the country's most popular alternative to Twitter. The phone sports a dedicated Sina microblog button, along with a set of bundled software from the po