Yahoo Inc. has closed Screen, the online-video portal that was the centerpiece of Chief Executive Marissa Mayer’s video strategy. The Internet company started Yahoo Screen in 2013 to merge professional content from media partners such as Walt Disney Co.’s ABC and Live Nation Entertainment Inc. with original programming. Yahoo spent more than $100 million producing its own shows, excluding the cost of employees. It also landed deals to syndicate high-profile shows such as reruns of “Saturday Night Live.” Ms. Mayer had hoped to bring in premium advertising.