Expose the type of device in MediaDeviceInfo

[youennf]

Chrome is currently exposing the type (builtin, bluetooth, maybe usb) in MediaDeviceInfo.label. This seems ok to expose like this but is difficult to use by web applications, if they would like to do so. Parsing the label might be hard and localisation might make this even more difficult to use. It might be interesting to split that information in its own attribute, whose value could be an enumeration. One potential use case would be a website showing the current device being used as an icon (instead of a label) according this information.