xds/eds: rewrite EDS policy using child policies

xds/internal/balancer/balancer.go

@@ -21,7 +21,9 @@ package balancer
 
 import (
 	_ "google.golang.org/grpc/xds/internal/balancer/cdsbalancer"    // Register the CDS balancer
+	_ "google.golang.org/grpc/xds/internal/balancer/clusterimpl"    // Register the xds_cluster_impl balancer
 	_ "google.golang.org/grpc/xds/internal/balancer/clustermanager" // Register the xds_cluster_manager balancer
 	_ "google.golang.org/grpc/xds/internal/balancer/edsbalancer"    // Register the EDS balancer
+	_ "google.golang.org/grpc/xds/internal/balancer/priority"       // Register the priority balancer
 	_ "google.golang.org/grpc/xds/internal/balancer/weightedtarget" // Register the weighted_target balancer
 )

xds/internal/balancer/balancergroup/balancergroup.go

@@ -183,7 +183,7 @@ type BalancerGroup struct {
 	cc        balancer.ClientConn
 	buildOpts balancer.BuildOptions
 	logger    *grpclog.PrefixLogger
-	loadStore load.PerClusterReporter
+	loadStore load.PerClusterReporter // TODO: delete this, no longer needed. It was used by EDS.
 
 	// stateAggregator is where the state/picker updates will be sent to. It's
 	// provided by the parent balancer, to build a picker with all the

xds/internal/balancer/edsbalancer/configbuilder_test.go

@@ -27,9 +27,6 @@ import (
 	"google.golang.org/grpc/xds/internal"
 	"google.golang.org/grpc/xds/internal/balancer/priority"
 	"google.golang.org/grpc/xds/internal/xdsclient"
-
-	_ "google.golang.org/grpc/xds/internal/balancer/clustermanager" // Register the xds_cluster_manager balancer
-	_ "google.golang.org/grpc/xds/internal/balancer/weightedtarget" // Register the weighted_target balancer
 )
 
 const (