forceDisconnect() {
    if (!this.isCasting_) {
      return;
    }

    this.rejectAllPromises_();

    if (shaka.cast.CastSender.session_) {
      this.removeListeners_();

      // This can throw if we've already been disconnected somehow.
      try {
        shaka.cast.CastSender.session_.stop(() => {}, () => {});
      } catch (error) {}

      shaka.cast.CastSender.session_ = null;
    }

    // Update casting status.
    this.onConnectionStatusChanged_();
  }
Forces the receiver app to shut down by disconnecting.  Does nothing if not
connected.