Here’s another high-profile ad win for Twitter as it gears up for its IPO: A big partnership with the NFL, which will bring video highlights and other content from America’s most popular sport to the social network. The pact is one of Twitter’s Amplify deals, which let TV programmers distribute short video clips, preceded by even shorter video ads, on the service. Both Twitter and the programmers are able to sell the ads, and share the revenue. Twitter has done a series of these deals, with networks and programmers like Viacom, Major League Baseball and Fox, starting last spring. Earlier this week it announced a pact with CBS. The revenue the deals generate for the company is nice. Also important: The messaging that surrounds them, which is that Twitter is trying to help advertisers and TV programmers build out the TV ecosystem — by directing people to TV sets, and by helping TV advertisers reinforce their TV spots — instead of trying to siphon money away from it.