Yahoo! announced Tuesday it is buying video-advertising platform, BrightRoll for about $640 million. Jim Cramer says Marissa Mayer is continuing to deliver. He says with BrightRoll, she made an acquisition in the one area where the margins have held up which is video. The plan is for Yahoo! to catch up with rivals in the video advertising space. But some top shareholders are unhappy with Mayer's efforts and want the company to merge with AOL with Tim Armstrong at the helm of the combined company. Cramer points out that Tim Armstrong's stock hasn't done anything this year. Cramer adds that Yahoo is flush with money from the Alibaba IPO and that can help to really grow the company by buying back stock and making strategic acquisitions.