Safeway Inc. spent about $350 million to build clinics in more than 800 of its supermarkets to offer blood tests by startup Theranos Inc. But the tests never began, the clinics are now used largely for flu shots and travel-related vaccines, and the two companies have been negotiating to officially dissolve their partnership, according to people familiar with the matter. Current and former Safeway executives said Theranos missed deadlines for the blood-testing rollout.