Clear the channel and endpoint_id in SetAddress for the XMPP channel.

remoting/protocol/jingle_messages.cc

Index: remoting/protocol/jingle_messages.cc
diff --git a/remoting/protocol/jingle_messages.cc b/remoting/protocol/jingle_messages.cc
index 57f9968e4ad3392e7a5df5445c94e5c2ddad4471..e9cf485aed75040f11e6899dd9d5d8d9659e0aed 100644
--- a/remoting/protocol/jingle_messages.cc
+++ b/remoting/protocol/jingle_messages.cc
@@ -202,6 +202,9 @@ void SetAddress(buzz::XmlElement* iqElement,
                 const SignalingAddress& address,
                 bool from) {
   if (address.empty()) {
+    iqElement->ClearAttr(GetQNameByField(Field::JID, from));
+    iqElement->ClearAttr(GetQNameByField(Field::CHANNEL, from));
+    iqElement->ClearAttr(GetQNameByField(Field::ENDPOINT_ID, from));

[Jamie, 2016/05/20 00:48:35]

I think it might be clearer to clear everything up-front with a comment
explaining that you want to start from a fresh state, regardless of the previous
address format. Then add in the components that make sense for the new format.

     return;
   }
 
@@ -212,6 +215,9 @@ void SetAddress(buzz::XmlElement* iqElement,
                        address.endpoint_id);
     const char* channel_str = ValueToName(kChannelTypes, address.channel);
     iqElement->AddAttr(GetQNameByField(Field::CHANNEL, from), channel_str);
+  } else {
+    iqElement->ClearAttr(GetQNameByField(Field::CHANNEL, from));
+    iqElement->ClearAttr(GetQNameByField(Field::ENDPOINT_ID, from));
   }
 }