code: public static LoadBalancer newHealthCheckingLoadBalancer(Factory factory, Helper helper) {
      HealthCheckingLoadBalancerFactory hcFactory =
          new HealthCheckingLoadBalancerFactory(
              factory, new ExponentialBackoffPolicy.Provider(),
              GrpcUtil.STOPWATCH_SUPPLIER);
      return hcFactory.newLoadBalancer(helper);
    }
docs: Creates a health-checking-capable LoadBalancer.  This method is used to implement
  health-checking-capable {@link Factory}s, which will typically written this way:
  
  <pre>
  public class HealthCheckingFooLbFactory extends LoadBalancer.Factory {
  // This is the original balancer implementation that doesn't have health checking
  private final LoadBalancer.Factory fooLbFactory;
  
  ...
  
  // Returns the health-checking-capable version of FooLb
  public LoadBalancer newLoadBalancer(Helper helper) {
  return HealthCheckingLoadBalancerUtil.newHealthCheckingLoadBalancer(fooLbFactory, helper);
  }
  }
  </pre>
  
  <p>As a requirement for the original LoadBalancer, it must call
  {@code Helper.createSubchannel()} from the {@link
  io.grpc.LoadBalancer.Helper#getSynchronizationContext() Synchronization Context}, or
  {@code createSubchannel()} will throw.
  
  @param factory the original factory that implements load-balancing logic without health
  checking
  @param helper the helper passed to the resulting health-checking LoadBalancer.