Legendary investor Warren Buffett has posted an impressive 21% year-to-date return for his flagship Berkshire Hathaway Inc in the first half of 2021.Here's a look at five stocks owned by Buffett and Berkshire Hathaway that could see strong gains in the second half of 2021.Aonreportedfirst-quarter revenue up 10% year-over-year, including organic revenue growth of 6%. The company’s margins improved and earnings per share grew 22% year-over-year. Aon announced a supply chain global protection plan