see https://www.w3.org/TR/2016/CR-mediacapture-streams-20160519/#idl-def-MediaDeviceKind in W3C spec
The MediaDevices interface provides access to connected media input devices like cameras and microphones, as well as screen sharing.
The MediaStream
see https://www.w3.org/TR/2013/WD-mediacapture-streams-20130903/#widl-MediaStream-onended in W3C spec
The MediaTrackSupportedConstraints dictionary establishes the list of constrainable properties recognized by the user agent or browser in its implementation of the MediaStreamTrack object.