China's retailers, already struggling because of an economic slowdown, got another jolt of bad news on Tuesday. Wal-Mart Stores announced it had finally received Chinese government approval for a proposal to buy a majority stake in Yihaodian, a Shanghai company that is a leader in the country's booming online retail industry. The fight for customers is heating up. In trading on Wednesday, the Hong Kong-listed shares of China's second-largest electronics retailer, Gome Electrical Appliance, fell as much as 11.1% after Liu Qiangdong, chairman of rival online retailer 360Buy Jingdong Mall, declared a three-year price war on his microblog.