type EngineCapabilityState = "unchecked" | "pending" | "supported" | "unsupported";Where a capability stands, in this order:
unchecked: nothing has asked for it to be measured, so it stays this way until something callscheckCapabilities()or runs a video check action.pending: it is being measured, and the answer arrives on its own.supportedorunsupported: the answer. A codec that stays silent through its own test counts asunsupported. A measurement the browser cuts off, as a background tab can, is no answer: the capability goes back tounchecked, and anyone still waiting gets a new measurement.