Fixup: Use GrpcUtil for flag retrieval and address other minor comments

Author: sauravzg

xds/src/main/java/io/grpc/xds/WeightedRoundRobinLoadBalancer.java

@@ -89,9 +89,6 @@
  *  See related documentation: https://cloud.google.com/service-mesh/legacy/load-balancing-apis/proxyless-configure-advanced-traffic-management#custom-lb-config
  */
 final class WeightedRoundRobinLoadBalancer extends MultiChildLoadBalancer {
-  @VisibleForTesting
-  static boolean enableCustomConfig =
-      Boolean.parseBoolean(System.getenv("GRPC_EXPERIMENTAL_WRR_CUSTOM_METRICS"));
 
   private static final LongCounterMetricInstrument RR_FALLBACK_COUNTER;
   private static final LongCounterMetricInstrument ENDPOINT_WEIGHT_NOT_YET_USEABLE_COUNTER;
@@ -335,8 +332,7 @@ public OrcaReportListener getOrCreateOrcaListener(float errorUtilizationPenalty,
         ImmutableList<String> metricNamesForComputingUtilization) {
       if (orcaReportListener != null
           && orcaReportListener.errorUtilizationPenalty == errorUtilizationPenalty
-          && Objects.equals(orcaReportListener.metricNamesForComputingUtilization,
-              metricNamesForComputingUtilization)) {
+          && orcaReportListener.metricNamesForComputingUtilization.equals(metricNamesForComputingUtilization)) {
         return orcaReportListener;
       }
       orcaReportListener =

xds/src/main/java/io/grpc/xds/WeightedRoundRobinLoadBalancerProvider.java

@@ -24,6 +24,7 @@
 import io.grpc.LoadBalancerProvider;
 import io.grpc.NameResolver.ConfigOrError;
 import io.grpc.Status;
+import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.JsonUtil;
 import io.grpc.xds.WeightedRoundRobinLoadBalancer.WeightedRoundRobinLoadBalancerConfig;
 import java.util.List;
@@ -105,10 +106,9 @@ private ConfigOrError parseLoadBalancingPolicyConfigInternal(Map<String, ?> rawC
     if (errorUtilizationPenalty != null) {
       configBuilder.setErrorUtilizationPenalty(errorUtilizationPenalty);
     }
-    if (metricNamesForComputingUtilization != null) {
-      if (WeightedRoundRobinLoadBalancer.enableCustomConfig) {
-        configBuilder.setMetricNamesForComputingUtilization(metricNamesForComputingUtilization);
-      }
+    if (metricNamesForComputingUtilization != null
+        && GrpcUtil.getFlag("GRPC_EXPERIMENTAL_WRR_CUSTOM_METRICS", false)) {
+      configBuilder.setMetricNamesForComputingUtilization(metricNamesForComputingUtilization);
     }
     return ConfigOrError.fromConfig(configBuilder.build());
   }

xds/src/test/java/io/grpc/xds/WeightedRoundRobinLoadBalancerProviderTest.java

@@ -113,19 +113,14 @@ public void parseLoadBalancingConfigDefaultValues() throws IOException {
 
   @Test
   public void parseLoadBalancingConfigCustomMetrics() throws IOException {
-    boolean originalEnableCustomConfig = WeightedRoundRobinLoadBalancer.enableCustomConfig;
-    WeightedRoundRobinLoadBalancer.enableCustomConfig = true;
-    try {
-      String lbConfig = "{\"metricNamesForComputingUtilization\" : [\"foo\", \"bar\"]}";
-      ConfigOrError configOrError = provider.parseLoadBalancingPolicyConfig(
-          parseJsonObject(lbConfig));
-      assertThat(configOrError.getConfig()).isNotNull();
-      WeightedRoundRobinLoadBalancerConfig config =
-          (WeightedRoundRobinLoadBalancerConfig) configOrError.getConfig();
-      assertThat(config.metricNamesForComputingUtilization).containsExactly("foo", "bar");
-    } finally {
-      WeightedRoundRobinLoadBalancer.enableCustomConfig = originalEnableCustomConfig;
-    }
+    System.setProperty("GRPC_EXPERIMENTAL_WRR_CUSTOM_METRICS", "true");
+    String lbConfig = "{\"metricNamesForComputingUtilization\" : [\"foo\", \"bar\"]}";
+    ConfigOrError configOrError = provider.parseLoadBalancingPolicyConfig(
+        parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    WeightedRoundRobinLoadBalancerConfig config =
+        (WeightedRoundRobinLoadBalancerConfig) configOrError.getConfig();
+    assertThat(config.metricNamesForComputingUtilization).containsExactly("foo", "bar");
   }