Add the URL attribute to cricket::Candiate.

webrtc/p2p/base/turnport.cc

Index: webrtc/p2p/base/turnport.cc
diff --git a/webrtc/p2p/base/turnport.cc b/webrtc/p2p/base/turnport.cc
index 7e0e64d6edacaf97751c3cbc56d18ca9a6f88dad..91ab62d798c2862dffac51cd8303cfea40e95d84 100644
--- a/webrtc/p2p/base/turnport.cc
+++ b/webrtc/p2p/base/turnport.cc
@@ -745,7 +745,7 @@ void TurnPort::OnAllocateSuccess(const rtc::SocketAddress& address,
              ProtoToString(server_address_.proto),  // The first hop protocol.
              "",  // TCP canddiate type, empty for turn candidates.
              RELAY_PORT_TYPE, GetRelayPreference(server_address_.proto),
-             server_priority_, true);
+             server_priority_, ReconstructedServerUrl(), true);
 }
 
 void TurnPort::OnAllocateError() {
@@ -1073,6 +1073,28 @@ bool TurnPort::SetEntryChannelId(const rtc::SocketAddress& address,
   return true;
 }
 
+std::string TurnPort::ReconstructedServerUrl() {
+  // draft-petithuguenin-behave-turn-uris-01
+  // turnURI       = scheme ":" turn-host [ ":" turn-port ]
+  //                 [ "?transport=" transport ]
+  // scheme        = "turn" / "turns"
+  // transport     = "udp" / "tcp" / transport-ext
+  // transport-ext = 1*unreserved
+  // turn-host     = IP-literal / IPv4address / reg-name
+  // turn-port     = *DIGIT
+  std::string scheme = "turn";
+  if (server_address_.proto == PROTO_SSLTCP ||
+      server_address_.proto == PROTO_TLS) {
+    scheme = "turns";
+  }
+  std::string transport = "tcp";
+  if (server_address_.proto == PROTO_UDP) {
+    transport = "udp";
+  }

[Taylor Brandstetter, 2017/02/10 01:58:46]

nit: A switch statement would be better here, so that if a new protocol is
added, there will be a compile warning and someone will know to update this
function.

[Zhi Huang, 2017/02/10 06:45:50]

Agreed. This would be better!

+  return scheme + ":" + server_address_.address.ToString() + "?transport=" +
+         transport;
+}
+
 TurnAllocateRequest::TurnAllocateRequest(TurnPort* port)
     : StunRequest(new TurnMessage()),
       port_(port) {