Nike shares tumbled for a second consecutive session on Friday after the sportswear giant warned that revenue will fall sharply this year and unveiled another round of layoffs as part of a sweeping cost-cutting plan.Shares of Nike fell more than 4% on Friday, extending losses after the company reported declining quarterly sales and laid out a weaker-than-expected outlook. The stock has now lost nearly 45% since the beginning of the year.Nike said fiscal first-quarter revenue fell 4% from a year earlier to $11.2 billion, with weakness in Greater China weighing on results despite growth in North America. Net income slipped…