async cast() {
    if (!this.sender_) {
      return;
    }
    // TODO: transfer manually-selected tracks?

    await this.sender_.cast();
    if (!this.localPlayer_) {
      // We've already been destroyed.
      return;
    }

    // Unload the local manifest when casting succeeds.
    await this.localPlayer_.unload();
  }
@return {!Promise} Resolved when connected to a receiver.  Rejected if the
  connection fails or is canceled by the user.
@export