Update references to the extended master secret draft.

It's now an RFC too.

Change-Id: I2aa7a862bf51ff01215455e87b16f259fc468490
Reviewed-on: https://boringssl-review.googlesource.com/7028
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/prf.go b/ssl/test/runner/prf.go
index 8521aba..f1b26de 100644
--- a/ssl/test/runner/prf.go
+++ b/ssl/test/runner/prf.go
@@ -153,7 +153,7 @@
 
 // extendedMasterFromPreMasterSecret generates the master secret from the
 // pre-master secret when the Triple Handshake fix is in effect. See
-// https://tools.ietf.org/html/draft-ietf-tls-session-hash-01
+// https://tools.ietf.org/html/rfc7627
 func extendedMasterFromPreMasterSecret(version uint16, suite *cipherSuite, preMasterSecret []byte, h finishedHash) []byte {
 	masterSecret := make([]byte, masterSecretLength)
 	prfForVersion(version, suite)(masterSecret, preMasterSecret, extendedMasterSecretLabel, h.Sum())