Tencent's (NASDAQOTH: TCEHY) stock surged nearly 1,100% between the end of 2010 and 2017 as the Chinese tech giant evolved into the top social networking player in China and the world's biggest video game publisher. However, the stock has slumped this year, tumbling about 20% peak-to-trough as of this writing.Tencent's big decline started in late March after its fourth-quarter report.