Add a new GetTlsUniqueChannelBinding method to SSLSocket, and implement nss version.

net/socket/ssl_client_socket_nss.cc

Index: net/socket/ssl_client_socket_nss.cc
diff --git a/net/socket/ssl_client_socket_nss.cc b/net/socket/ssl_client_socket_nss.cc
index 9d0eea2a070398024e9dd5e34283ce1e2971e930..9b2aed145667c9585bdea1eb0343076e661b56af 100644
--- a/net/socket/ssl_client_socket_nss.cc
+++ b/net/socket/ssl_client_socket_nss.cc
@@ -2824,6 +2824,21 @@ int SSLClientSocketNSS::ExportKeyingMaterial(const base::StringPiece& label,
   return OK;
 }
 
+int SSLClientSocketNSS::GetTlsUniqueChannelBinding(unsigned char* out,
+                                                   unsigned int *outlen,
+                                                   unsigned int outlen_max) {
+  if (!IsConnected())
+    return ERR_SOCKET_NOT_CONNECTED;
+  SECStatus result = SSL_GetChannelBinding(nss_fd_,
+                                           SSL_CHANNEL_BINDING_TLS_UNIQUE,
+                                           out, outlen, outlen_max);
+  if (result != SECSuccess) {
+    LogFailedNSSFunction(net_log_, "SSL_GetChannelBinding", "");
+    return MapNSSError(PORT_GetError());
+  }
+  return OK;
+}
+
 SSLClientSocket::NextProtoStatus
 SSLClientSocketNSS::GetNextProto(std::string* proto,
                                  std::string* server_protos) {