VIENTIANE, Laos — Southeast Asian defense chiefs met Thursday with their counterparts from China, the United States and other nations in Laos for security talks, which come as Beijing’s increasingly assertive stance in its claim to most of the South China Sea is leading to more confrontations. The closed-door talks put U.S. Secretary of Defense Lloyd Austin and Chinese Defense Minister Dong Jun in the same room, a day after Dong refused a request to meet with Austin one-on-one on the sidelines