As many as 400,000 California undocumented farmworkers may get a fast track to legal status under a potential landmark accord between the agricultural industry and the United Farm Workers Union. The agreement, hashed out with key guidance from U.S. Sen. Dianne Feinstein, D- Calif., stands to be a major component in sweeping immigration legislation introduced Wednesday in the Senate. Backers hail the farm labor accord, which still faces an arduous path through Congress, as an elixir to a significant worker shortage in California’s $44.3 billion agricultural industry and beyond.