Dark Knight clears $400 million at record pace By Steve Gorman, ReutersLOS ANGELES (Reuters) - Batman sequel "The Dark Knight" smashed yet another Hollywood record as it cleared the $400 million domestic box office mark in 18 days, less than half the time it took "Shrek 2" to reach that milestone, Warner Bros. Pictures said Tuesday.After a third straight weekend at No. 1 in U.S. and Canadian theaters -- grossing $42.7 million Friday through Sunday -- "Dark Knight" amassed $6.3 million Monday to bring its domestic tally to $400.03 million, the Time Warner Inc.-owned movie distributor reported.The previous record holder, the computer-animated storybook spoof "Shrek 2," crossed the $400 million mark in 43 days back in 2004, according to box office watcher Media By Numbers.Warner Bros. has said it expects "Dark Knight" to add at least another $100 million to its North American ticket sales, surpassing the $461 million haul of 1977's "Star Wars" and its two reissues. "Star Wars" ranks as the No. 2 movie of all time in the United States and Canada.While "Dark Knight" appears destined to become only the second movie to gross $500 million domestically, the $601 million record held by 1997's "Titanic" seems unlikely to sink, ...