diff --git a/bar_tobeRemoved.go b/bar_tobeRemoved.go
new file mode 100644
index 000000000000..8b6a4fadae69
--- /dev/null
+++ b/bar_tobeRemoved.go
@@ -0,0 +1,78 @@
+package grpc
+
+import (
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////       To b or not to b.       /////////////////////////
+//////////////////////////////////////////////////////////////////////////////
+
+// newSubConnection adds a new addrConn to clientconn, and returns a wrapper
+// subConn for balancer.
+func (cc *ClientConn) newSubConnection(addrs []resolver.Address, opts balancer.NewSubConnectionOptions) (*addrConn, error) {
+	grpclog.Printf("creating new subconn, addrs[0]: %v\n", addrs[0])
+	ac, err := cc.resetAddrConn(addrs[0], false, nil)
+	if err != nil {
+		// TODO what to do?
+		grpclog.Printf("neverrrrrrrr got err when resetting addrconn %v", err)
+		return nil, err
+	}
+	return ac, nil
+}
+
+// removeSubConnection removes the addrConn in the subConn from clientConn.
+// It also tears down the ac with the given error.
+func (cc *ClientConn) removeSubConnection(ac *addrConn, err error) {
+	grpclog.Printf("removing new subconn")
+	cc.mu.Lock()
+	delete(cc.conns, ac)
+	cc.mu.Unlock()
+	ac.tearDown(err)
+}
+
+func (cc *ClientConn) updatePicker(p balancer.Picker) {
+	grpclog.Printf("cc.updatePicker: %p", p)
+	// TODO add a goroutine and sync it.
+	cc.pmu.Lock()
+	cc.picker = p
+	cc.pmu.Unlock()
+}
+
+// ccBalancerWrapper is a wrapper on top of cc for balancers.
+// It implements balancer.ClientConnection interface.
+type ccBalancerWrapper struct {
+	cc *ClientConn
+}
+
+func (ccb *ccBalancerWrapper) NewSubConnection(addrs []resolver.Address, opts balancer.NewSubConnectionOptions) (balancer.SubConnection, error) {
+	return ccb.cc.newSubConnection(addrs, opts)
+}
+
+func (ccb *ccBalancerWrapper) RemoveSubConnection(sc balancer.SubConnection) {
+	ac, ok := sc.(*addrConn)
+	if !ok {
+		// TODO log or error?
+		return
+	}
+	ccb.cc.removeSubConnection(ac, errConnClosing)
+}
+
+func (ccb *ccBalancerWrapper) UpdateBalancerState(s connectivity.State, p balancer.Picker) {
+	ccb.cc.updatePicker(p)
+}
+
+func (ccb *ccBalancerWrapper) Target() string {
+	return ccb.cc.target
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////       To a or not to a.       /////////////////////////
+//////////////////////////////////////////////////////////////////////////////
+
+func (ac *addrConn) UpdateAddresses([]resolver.Address) {}
+
+func (ac *addrConn) Connect() {}
diff --git a/clientconn.go b/clientconn.go
index 45ea87eb61e8..db3a25e52541 100644
--- a/clientconn.go
+++ b/clientconn.go
@@ -673,15 +673,15 @@ func (ac *addrConn) connect(block bool) error {
 	}
 	if !ac.dopts.insecure {
 		if ac.dopts.copts.TransportCredentials == nil {
-			return errNoTransportSecurity
+			return nil, errNoTransportSecurity
 		}
 	} else {
 		if ac.dopts.copts.TransportCredentials != nil {
-			return errCredentialsConflict
+			return nil, errCredentialsConflict
 		}
 		for _, cd := range ac.dopts.copts.PerRPCCredentials {
 			if cd.RequireTransportSecurity() {
-				return errTransportCredentialsMissing
+				return nil, errTransportCredentialsMissing
 			}
 		}
 	}
@@ -692,9 +692,9 @@ func (ac *addrConn) connect(block bool) error {
 				ac.tearDown(err)
 			}
 			if e, ok := err.(transport.ConnectionError); ok && !e.Temporary() {
-				return e.Origin()
+				return nil, e.Origin()
 			}
-			return err
+			return nil, err
 		}
 		// Start to monitor the error status of transport.
 		go ac.transportMonitor()
@@ -712,7 +712,7 @@ func (ac *addrConn) connect(block bool) error {
 			ac.transportMonitor()
 		}()
 	}
-	return nil
+	return ac, nil
 }
 
 // tryUpdateAddrs tries to update ac.addrs with the new addresses list.
@@ -905,7 +905,7 @@ func (ac *addrConn) resetTransport(drain bool) error {
 		return errConnClosing
 	}
 	oldState := ac.state
-	ac.state = connectivity.Connecting
+	ac.state = connectivity.TransientFailure
 	ac.csEvltr.recordTransition(oldState, ac.state)
 	if ac.cc.balancer != nil {
 		ac.cc.balancer.HandleSubConnStateChange(ac.acbw, ac.state)
diff --git a/doc.go b/doc.go
index 187adbb117f2..a5098bb33a7e 100644
--- a/doc.go
+++ b/doc.go
@@ -22,3 +22,9 @@ Package grpc implements an RPC system called gRPC.
 See grpc.io for more information about gRPC.
 */
 package grpc // import "google.golang.org/grpc"
+
+import (
+	_ "google.golang.org/grpc/balancer"     // test build
+	_ "google.golang.org/grpc/connectivity" // test build
+	_ "google.golang.org/grpc/resolver"     // test build
+)