static fromRealEvent(event) {
    const fakeEvent = new shaka.util.FakeEvent(event.type);
    for (const key in event) {
      Object.defineProperty(fakeEvent, key, {
        value: event[key],
        writable: true,
        enumerable: true,
      });
    }
    return fakeEvent;
  }
@param {!Event} event
@return {!shaka.util.FakeEvent}