[Chromoting] Add SessionPlugin in JingleSession

remoting/protocol/session.h

Index: remoting/protocol/session.h
diff --git a/remoting/protocol/session.h b/remoting/protocol/session.h
index 865af39b3a789f594b61bf76364ecf0b46569e9e..1ee3f7c00ffa2c6aae2e3fa362d59106628a6b96 100644
--- a/remoting/protocol/session.h
+++ b/remoting/protocol/session.h
@@ -5,6 +5,7 @@
 #ifndef REMOTING_PROTOCOL_SESSION_H_
 #define REMOTING_PROTOCOL_SESSION_H_
 
+#include <memory>
 #include <string>
 
 #include "base/macros.h"
@@ -15,6 +16,7 @@
 namespace remoting {
 namespace protocol {
 
+class SessionPlugin;
 class Transport;
 
 // Session is responsible for initializing and authenticating both incoming and
@@ -85,6 +87,10 @@ class Session {
   // is being closed due to an error.
   virtual void Close(ErrorCode error) = 0;
 
+  // Attaches a SessionPlugin to handle attachments. |plugin| should not be an
+  // empty std::unique_ptr.
+  virtual void Attach(std::unique_ptr<SessionPlugin> plugin) = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(Session);
 };