Support a user-provided string for the TLS ALPN extension.

webrtc/pc/iceserverparsing.cc

 /*
  *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 239 matching lines @@
         }
         socket_address.SetResolvedIP(ip);
       }
       cricket::RelayServerConfig config = cricket::RelayServerConfig(
           socket_address, username, server.password, turn_transport_type);
       if (server.tls_cert_policy ==
           PeerConnectionInterface::kTlsCertPolicyInsecureNoCheck) {
         config.tls_cert_policy =
             cricket::TlsCertPolicy::TLS_CERT_POLICY_INSECURE_NO_CHECK;
       }
+      config.tls_alpn_protocols = server.tls_alpn_protocols;
+
       turn_servers->push_back(config);
       break;
     }
     default:
       // We shouldn't get to this point with an invalid service_type, we should
       // have returned an error already.
       RTC_NOTREACHED() << "Unexpected service type";
       return RTCErrorType::INTERNAL_ERROR;
   }
   return RTCErrorType::NONE;
@@ skipping 32 matching lines @@
   // are performed in a well-defined order.
   int priority = static_cast<int>(turn_servers->size() - 1);
   for (cricket::RelayServerConfig& turn_server : *turn_servers) {
     // First in the list gets highest priority.
     turn_server.priority = priority--;
   }
   return RTCErrorType::NONE;
 }
 
 }  // namespace webrtc