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

webrtc/p2p/base/turnport.h

Index: webrtc/p2p/base/turnport.h
diff --git a/webrtc/p2p/base/turnport.h b/webrtc/p2p/base/turnport.h
index abdaa3dcb433b7f1d508a2a229e8240db445251e..46200a988c601ffb669f84f11a219dd4fc554f13 100644
--- a/webrtc/p2p/base/turnport.h
+++ b/webrtc/p2p/base/turnport.h
@@ -69,10 +69,11 @@ class TurnPort : public Port {
                           const ProtocolAddress& server_address,
                           const RelayCredentials& credentials,
                           int server_priority,
-                          const std::string& origin) {
+                          const std::string& origin,
+                          const std::vector<std::string>& tls_alpn_protocols) {
     return new TurnPort(thread, factory, network, min_port, max_port, username,
                         password, server_address, credentials, server_priority,
-                        origin);
+                        origin, tls_alpn_protocols);
   }
 
   virtual ~TurnPort();
@@ -95,6 +96,10 @@ class TurnPort : public Port {
     tls_cert_policy_ = tls_cert_policy;
   }
 
+  virtual std::vector<std::string> GetTlsAlpnProtocols() const {
+    return tls_alpn_protocols_;
+  }
+
   virtual void PrepareAddress();
   virtual Connection* CreateConnection(
       const Candidate& c, PortInterface::CandidateOrigin origin);
@@ -186,7 +191,8 @@ class TurnPort : public Port {
            const ProtocolAddress& server_address,
            const RelayCredentials& credentials,
            int server_priority,
-           const std::string& origin);
+           const std::string& origin,
+           const std::vector<std::string>& alpn_protocols);
 
  private:
   enum {
@@ -266,6 +272,7 @@ class TurnPort : public Port {
 
   ProtocolAddress server_address_;
   TlsCertPolicy tls_cert_policy_ = TlsCertPolicy::TLS_CERT_POLICY_SECURE;
+  std::vector<std::string> tls_alpn_protocols_;
   RelayCredentials credentials_;
   AttemptedServerSet attempted_server_addresses_;