An automotive venture backed by China tech giant Tencent aims to launch an electric self-driving car before 2020, entering a crowded field dominated by US-based Tesla Motors, the chief executive told Reuters on Tuesday. Future Mobility, backed by Tencent and Hon Hai Precision Industries, is one of an expanding field of China-backed ventures that aim to take on Tesla Motors Inc as green energy car sales boom in China. Although the venture seeks to produce…