hide() {
    if (this.timeout_) {
      clearTimeout(this.timeout_);
      this.timeout_ = null;
    }

    this.container_.remove();
    // Remove all children in case there was sensitive content shown that we
    // don't want to leave laying around.
    this.container_.textContent = '';
  }
Hide the active notification immediately.

Useful when we show a message for an event with an unknown end time.