SAN FRANCISCO — Home device maker Nest Labs is adding Google’s facial recognition technology to a camera-equipped doorbell and rolling out a security system in an attempt to end its history of losses. The products announced Wednesday expand upon the internet-connected thermostats, smoke detectors and stand-alone security cameras that Nest has been selling since its inception six years ago. Although Nest has been among the early leaders in the effort to make home appliances as intelligent as people’s smartphones, it hasn’t been able to make money to the frustration of its corporate parent, Alphabet.