The world's biggest brewer, Anheuser-Busch InBev NV, began trading on the Johannesburg Stock Exchange Friday, the latest in a series of multinational heavyweights to complete a secondary listing in South Africa, strengthening the local bourse even as the broader economy continues to decelerate. Mega-brewer AB InBev's listing is the most recent step in its more than $100 billion quest to acquire SABMiller PLC, which has its ancestral home in South Africa.