[Chromoting] Add SessionPlugin in JingleSession

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 480a2c252d6aba242575d0b21217da0b67dc63c2..89a288a0bdf8791cc9d611b155b1bd067d3dce6a 100644
--- a/remoting/protocol/jingle_messages.cc
+++ b/remoting/protocol/jingle_messages.cc
@@ -9,6 +9,7 @@
 #include "remoting/base/constants.h"
 #include "remoting/protocol/content_description.h"
 #include "remoting/protocol/name_value_map.h"
+#include "remoting/protocol/session_plugin.h"
 #include "remoting/signaling/jid_util.h"
 #include "remoting/signaling/remoting_bot.h"
 #include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
@@ -343,7 +344,7 @@ bool JingleMessage::ParseXml(const buzz::XmlElement* stanza,
   }
 
   const XmlElement* attachments_tag =
-      jingle_tag->FirstNamed(QName(kChromotingXmlNamespace, "attachments"));
+      SessionPlugin::FindAttachments(*jingle_tag);
   if (attachments_tag) {
     attachments.reset(new XmlElement(*attachments_tag));
   } else {