The National Football League's 32 team owners agreed Dec. 7 to provide $300 million in financing for an estimated $1.2-billion football stadium in the New Jersey Meadowlands to be shared by the New York Giants and Jets. Team owners John Mara, Steve Tisch and Woody Johnson say the hope to begin construction in spring. They have not yet chosen a contractor, with bidders including Skanska Building USA and Bovis Lend Lease, says a source.