Favor private types/fields

- Switch `upgradableRoundTripper` and `upgradeNextProto` to be private. We
can always change these to be public if/when we move logic into another
package.

[cloudfoundry/routing-release#200]

Author: Gerg

http/h2_bundle.go

@@ -230,9 +230,6 @@ type Transport struct {
 	// automatically.
 	TLSNextProto map[string]func(authority string, c *tls.Conn) RoundTripper
 
-	// TODO(gerg): Consider this public interface change for Transport
-	UpgradeNextProto map[string]func(string, *tls.Conn) UpgradableRoundTripper
-
 	// ProxyConnectHeader optionally specifies headers to send to
 	// proxies during CONNECT requests.
 	ProxyConnectHeader Header
@@ -259,6 +256,7 @@ type Transport struct {
 	nextProtoOnce      sync.Once
 	h2transport        h2Transport // non-nil if http2 wired up
 	tlsNextProtoWasNil bool        // whether TLSNextProto was nil when the Once fired
+	upgradeNextProto   map[string]func(string, *tls.Conn) upgradableRoundTripper
 
 	// ForceAttemptHTTP2 controls whether HTTP/2 is enabled when a non-zero
 	// Dial, DialTLS, or DialContext func or TLSClientConfig is provided.
@@ -540,10 +538,9 @@ func (t *Transport) roundTrip(req *Request) (*Response, error) {
 			resp, err = pconn.alt.RoundTrip(req)
 		} else {
 			resp, err = pconn.roundTrip(treq)
-
-			if err == nil && resp.StatusCode == StatusSwitchingProtocols {
+			if err == nil && resp.isProtocolSwitch() {
 				upgradeProto := resp.Header.Get("Upgrade")
-				if upgradeFn, ok := t.UpgradeNextProto[upgradeProto]; ok {
+				if upgradeFn, ok := t.upgradeNextProto[upgradeProto]; ok {
 					t2 := upgradeFn(cm.targetAddr, pconn.conn.(*tls.Conn))
 					pconn.alt = t2
 					resp, err = t2.completeUpgrade(req)
@@ -2154,8 +2151,6 @@ func (pc *persistConn) readResponse(rc requestAndChan, trace *httptrace.ClientTr
 		break
 	}
 	if resp.isProtocolSwitch() {
-		// TODO(gerg): This might be an interesting place to put some upgrade logic
-
 		resp.Body = newReadWriteCloserBody(pc.br, pc.conn)
 	}