This API provides network performance information to developers, as perceived by the UA, in a format that’s easy to consume and act upon: UA monitors latency and throughput of recent requests and provides estimates for effective RTT, throughput, and connection type that developers should optimize for - e.g. if the recently observed latency and/or throughput is low, the effective connection type will be mapped to a “low” value like 2G or 3G, regardless of the underlying network technology.
Samples: https://googlechrome.github.io/samples/network-information/