message: added toJSON method
diff: @@ -20,4 +20,14 @@ export class VideoInputDevice implements MediaDeviceInfo {
  public constructor(public deviceId: string, public label: string, groupId?: string) {
  this.groupId = groupId || undefined;
  }
  +
  + /** @inheritdoc */
  + toJSON() {
  + return {
  + kind: this.kind,
  + groupId: this.groupId,
  + deviceId: this.deviceId,
  + label: this.label,
  + };
  + }
  }
  