“Acknowledging he lacks direct evidence of discrimination, however, Mr. Waggoner contends, and we agree, the burden-shifting framework established by McDonnell Douglas Corp. v.( Green … (1973), applies here,” Judge Veronica S. Rossman wrote on behalf of the unanimous panel. “Under that framework, Mr. Waggoner first must establish a prima facie case of age discrimination … The burden then shifts to Frito-Lay to proffer a legitimate, non discriminatory reason for failing to promote Mr. Waggoner to the Processing Manager position.