code: void removeLocality(final Locality locality) {
      ClientLoadCounter counter = localityLoadCounters.get(locality);
      checkState(counter != null && counter.isActive(),
          "No active ClientLoadCounter for locality %s exists", locality);
      counter.setActive(false);
    }
docs: Deactivate the {@link ClientLoadCounter} for the provided locality in by this
  {@link XdsLoadReportStore}. Inactive {@link ClientLoadCounter}s are for localities
  no longer exposed by the remote balancer. This method needs to be called at
  locality updates only for localities newly removed from balancer discovery responses.
  This method should be called in the same synchronized context that
  {@link XdsLoadBalancer#helper#getSynchronizationContext} returns.