Currently, calling navigator.mediaDevices.getDisplayMedia() with no parameters throws a TypeError.

But according to the spec, the first and only parameter is optional.
See: https://www.w3.org/TR/screen-capture/#mediadevices-additions

Also, according to the spec, the first parameter type is DisplayMediaStreamConstraints, which defaults to:
{
  video = true;
  audio = false;
}
See: https://www.w3.org/TR/screen-capture/#dom-displaymediastreamconstraints

Expected behavior:
Calling getDisplayMedia() with no parameters will not throw an error, but will use the defaults of DisplayMediaStreamConstraints.