onFirstCastStateUpdate_() {
    const type = this.videoProxy_['paused'] ? 'pause' : 'play';
    const fakeEvent = new shaka.util.FakeEvent(type);
    this.videoEventTarget_.dispatchEvent(fakeEvent);
  }
Dispatch a synthetic play or pause event to ensure that the app correctly
knows that the player is playing, if joining an existing receiver.
@private