core: Validate load-balancing policy name early in ManagedChannelBuilder (#12695)

Author: themechbro

api/src/main/java/io/grpc/ManagedChannelBuilder.java

@@ -17,6 +17,8 @@
 package io.grpc;
 
 import com.google.common.base.Preconditions;
+
+import java.nio.channels.Channel;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
@@ -280,13 +282,12 @@ public T useTransportSecurity() {
    * @return this
    * @since 1.18.0
    */
-  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771")
+ @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771")
   public T defaultLoadBalancingPolicy(String policy) {
-    Preconditions.checkArgument(
-      LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null,
-      "invalid load balancing policy %s", policy
-    );
-    throw new UnsupportedOperationException();
+    Preconditions.checkArgument( // 4 spaces
+        LoadBalancerRegistry.getDefaultRegistry().getProvider(policy) != null, // 8 spaces
+        "invalid load balancing policy %s", policy); // 8 spaces
+    throw new UnsupportedOperationException(); // 4 spaces
   }
 
   /**

core/src/main/java/io/grpc/internal/ManagedChannelImplBuilder.java

@@ -213,7 +213,6 @@ public static ManagedChannelBuilder<?> forTarget(String target) {
   private boolean recordRetryMetrics = true;
   private boolean tracingEnabled = true;
   List<MetricSink> metricSinks = new ArrayList<>();
-
   /**
    * An interface for Transport implementors to provide the {@link ClientTransportFactory}
    * appropriate for the channel.