code: function() {
          // Get time until expiration minus the refresh offset.
          var waitInterval =
              self.stsTokenManager_.getExpirationTime() - goog.now() -
              fireauth.TokenRefreshTime.OFFSET_DURATION;
          // Set to zero if wait interval is negative.
          return waitInterval > 0 ? waitInterval : 0;
        }
docs: Return next time to run with offset applied.