public function revokeToken() {
    $accessToken = $this->storage->get();
    if ($accessToken) {
      $tokenObj = json_decode($accessToken);
      try {
        $this->client->revokeToken($tokenObj->refresh_token);
        $this->storage->delete();
      } catch (Google_AuthException $e) {
        $this->errorMsg = $e->getMessage();
      }
    }
    // Keep things pretty. Removes the auth code from the URL.
    header("Location: $this->controllerUrl");
  }