dispatchEmsgEvent_(region) {
    const eventName = shaka.util.FakeEvent.EventName.Emsg;
    const emsg = region.emsg;
    const data = new Map().set('detail', emsg);
    this.dispatchEvent(shaka.Player.makeEvent_(eventName, data));
  }
Construct and fire a Player.EMSG event

@param {shaka.extern.EmsgTimelineRegionInfo} region
@private