House Speaker Nancy Pelosi (D-Calif.) had lunch with two top executives from Taiwan’s biggest semiconductor manufacturer during her whistle-stop tour of the island, underscoring how vital computer chips have become to U.S. national security. In a Facebook post on Wednesday, Taiwanese President Tsai Ing-wen said that Pelosi and she attended a lunch with Morris Chang, the founder of Taiwan Semiconductor Manufacturing Company, and its chairman, Mark Liu, as well as Cheng Jianzhong, vice chairman of electronics manufacturer Pegatron. “Everyone exchanged views on the deepening of cooperation between Taiwan and the United States in various fields. . . . Taiwan and...